drm/amdgpu: use drm_mode_vrefresh() rather than mode->vrefresh

This is a port of radeon commit:
3d2d98ee1af0cf6eebfbd6bff4c17d3601ac1284
drm/radeon: use drm_mode_vrefresh() rather than mode->vrefresh
to amdgpu.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
1 file changed