drm/amd/display: Lock the CRTC when setting CRC source

[Why]
We need to ensure that we're holding the lock on the CRTC when setting
the CRC source since we're modifying the CRTC state directly.

We also need to wait for any outstanding non-blocking commits to finish
so they aren't reading state that's potentially being modified -
non-blocking commits don't hold the CRTC lock while doing commit tail
work.

[How]
Lock the CRTC using its mutex. While holding the lock check if there's
any commit active on the CRTC - if there is, it's non-blocking and
we should wait until it's finished by waiting for hw_done to be
signaled since that's the last point where we touch CRTC state.

Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: David Francis <David.Francis@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>