drivers: gpu: Add static keyword to the definition of KMS_INVALID_IOCTL in radeon_kms.c

drivers: gpu: Add static keyword to the definition of KMS_INVALID_IOCTL in radeon_kms.c

Add static keyword to the definition of KMS_INVALID_IOCTL(name) in
radeon_kms.c because the functions passed to it as arguments are not
used anywhere else.

This eliminates the following warnings in drm/radeon/radeon_kms.c:
drivers/gpu/drm/radeon/radeon_kms.c:719:1: warning: no previous prototype for ‘radeon_cp_init_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:720:1: warning: no previous prototype for ‘radeon_cp_start_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:721:1: warning: no previous prototype for ‘radeon_cp_stop_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:722:1: warning: no previous prototype for ‘radeon_cp_reset_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:723:1: warning: no previous prototype for ‘radeon_cp_idle_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:724:1: warning: no previous prototype for ‘radeon_cp_resume_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:725:1: warning: no previous prototype for ‘radeon_engine_reset_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:726:1: warning: no previous prototype for ‘radeon_fullscreen_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:727:1: warning: no previous prototype for ‘radeon_cp_swap_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:728:1: warning: no previous rototype for ‘radeon_cp_clear_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:729:1: warning: no previous prototype for ‘radeon_cp_vertex_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:730:1: warning: no previous rototype for ‘radeon_cp_indices_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:731:1: warning: no previous prototype for ‘radeon_cp_texture_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:732:1: warning: no previous prototype for ‘radeon_cp_stipple_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:733:1: warning: no previous prototype for ‘radeon_cp_indirect_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:734:1: warning: no previous prototype for ‘radeon_cp_vertex2_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:735:1: warning: no previous prototype for ‘radeon_cp_cmdbuf_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:736:1: warning: no previous prototype for ‘radeon_cp_getparam_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:737:1: warning: no previous prototype for ‘radeon_cp_flip_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:738:1: warning: no previous prototype for ‘radeon_mem_alloc_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:739:1: warning: no previous prototype for ‘radeon_mem_free_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:740:1: warning: no previous rototype for ‘radeon_mem_init_heap_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:741:1: warning: no previous rototype for ‘radeon_irq_emit_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:742:1: warning: no previous prototype for ‘radeon_irq_wait_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:743:1: warning: no previous rototype for ‘radeon_cp_setparam_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:744:1: warning: no previous prototype for ‘radeon_surface_alloc_kms’ [-Wmissing-prototypes]
drivers/gpu/drm/radeon/radeon_kms.c:745:1: warning: no previous prototype for ‘radeon_surface_free_kms’ [-Wmissing-prototypes]

Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>