drm/modes: drop return value from drm_display_mode_from_videomode

It never fails and no one ever checked anyway.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --cc drivers/gpu/drm/drm_modes.c
Simple merge

diff --cc include/drm/drm_modes.h
Simple merge