drm/amd/display: Fix GSL acquire

[Why]
After locking refactor GSL is not acquired properly
resulting in immediate flip issues.

[How]
Do not copy old GSL state anymore since GSL is acquired
earlier now.

Signed-off-by: Aric Cyr <aric.cyr@amd.com>
Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>