[media] s5p_mfc_ctrl: add missing s5p_mfc_ctrl.h header

[media] s5p_mfc_ctrl: add missing s5p_mfc_ctrl.h header

That gets rid of the following warnings:

drivers/media/platform/s5p-mfc/s5p_mfc_ctrl.c:119:5: warning: no previous prototype for 's5p_mfc_release_firmware' [-Wmissing-prototypes]
 int s5p_mfc_release_firmware(struct s5p_mfc_dev *dev)
     ^
drivers/media/platform/s5p-mfc/s5p_mfc_ctrl.c:132:5: warning: no previous prototype for 's5p_mfc_reset' [-Wmissing-prototypes]
 int s5p_mfc_reset(struct s5p_mfc_dev *dev)
     ^
drivers/media/platform/s5p-mfc/s5p_mfc_ctrl.c:214:5: warning: no previous prototype for 's5p_mfc_init_hw' [-Wmissing-prototypes]
 int s5p_mfc_init_hw(struct s5p_mfc_dev *dev)
     ^
drivers/media/platform/s5p-mfc/s5p_mfc_ctrl.c:291:6: warning: no previous prototype for 's5p_mfc_deinit_hw' [-Wmissing-prototypes]
 void s5p_mfc_deinit_hw(struct s5p_mfc_dev *dev)
      ^
drivers/media/platform/s5p-mfc/s5p_mfc_ctrl.c:301:5: warning: no previous prototype for 's5p_mfc_sleep' [-Wmissing-prototypes]
 int s5p_mfc_sleep(struct s5p_mfc_dev *dev)
     ^
drivers/media/platform/s5p-mfc/s5p_mfc_ctrl.c:330:5: warning: no previous prototype for 's5p_mfc_wakeup' [-Wmissing-prototypes]
 int s5p_mfc_wakeup(struct s5p_mfc_dev *dev)
     ^
drivers/media/platform/s5p-mfc/s5p_mfc_ctrl.c:378:5: warning: no previous prototype for 's5p_mfc_open_mfc_inst' [-Wmissing-prototypes]
 int s5p_mfc_open_mfc_inst(struct s5p_mfc_dev *dev, struct s5p_mfc_ctx *ctx)
     ^
drivers/media/platform/s5p-mfc/s5p_mfc_ctrl.c:420:6: warning: no previous prototype for 's5p_mfc_close_mfc_inst' [-Wmissing-prototypes]
 void s5p_mfc_close_mfc_inst(struct s5p_mfc_dev *dev, struct s5p_mfc_ctx *ctx)
      ^

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>