drm/msm/disp: mdp_format: fix all kernel-doc warnings

drm/msm/disp: mdp_format: fix all kernel-doc warnings

Correct and add kernel-doc comments to eliminate all warnings:

Warning: ../drivers/gpu/drm/msm/disp/mdp_format.h:27 This comment starts
 with '/**', but isn't a kernel-doc comment.
Warning: ../drivers/gpu/drm/msm/disp/mdp_format.h:64 struct member
 'bpc_a' not described in 'msm_format'
Warning: ../drivers/gpu/drm/msm/disp/mdp_format.h:64 struct member
 'bpc_b_cb' not described in 'msm_format'
Warning: ../drivers/gpu/drm/msm/disp/mdp_format.h:64 struct member
 'bpc_g_y' not described in 'msm_format'
Warning: ../drivers/gpu/drm/msm/disp/mdp_format.h:64 struct member
 'bpc_r_cr' not described in 'msm_format'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/695650/
Link: https://lore.kernel.org/r/20251219184638.1813181-2-rdunlap@infradead.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>