commit d8e24525 upstream.

Seems to cause problems with certain DP monitors.

Bug:
https://bugs.freedesktop.org/show_bug.cgi?id=40699Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[bwh: Backported to 3.2: s/radeon_crtc->//]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>