drm/imx: Constify function pointer structs

drm/imx: Constify function pointer structs

Moves a bunch of junk to .rodata from .data.

 drivers/gpu/drm/imx/imxdrm.ko:
-.rodata                      624
+.rodata                      652
-.data                        372
+.data                        344

 drivers/gpu/drm/imx/imx-ipuv3-crtc.ko:
-.rodata                      224
+.rodata                      280
-.data                        184
+.data                        128

 drivers/gpu/drm/imx/imx-ldb.ko:
-.rodata                      660
+.rodata                      784
-.data                        240
+.data                        116

 drivers/gpu/drm/imx/imx-tve.ko:
-.rodata                      400
+.rodata                      524
-.data                        416
+.data                        292

 drivers/gpu/drm/imx/parallel-display.ko:
-.rodata                      400
+.rodata                      524
-.data                        216
+.data                         92

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1450178476-26284-22-git-send-email-boris.brezillon@free-electrons.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>