On IGT, there is a test named amd_hotplug, and when the subtest basic is
executed on DCN31, we get the following error:

[drm] *ERROR* [CRTC:71:crtc-0] flip_done timed out
[drm] *ERROR* flip_done timed out
[drm] *ERROR* [CRTC:71:crtc-0] commit wait timed out
[drm] *ERROR* flip_done timed out
[drm] *ERROR* [CONNECTOR:88:DP-1] commit wait timed out
[drm] *ERROR* flip_done timed out
[drm] *ERROR* [PLANE:59:plane-3] commit wait timed out

After enable the page flip log with the below command:

 echo -n 'format "[PFLIP]" +p' > /sys/kernel/debug/dynamic_debug/control

It is possible to see that the flip was submitted, but DC never replied
back, which generates time-out issues. This is an indication that the
HUBP surface flip is missing. This commit fixes this issue by adding
hubp1_set_flip_int to DCN31.
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>