drm/amd/display: Update GSL state if leaving immediate flip

[Why]
We should leave GSL if we're not doing immediate flip no matter if
we're doing pipe split or not

[How]
Check for updating GSL state whenever we're not doing
immediate flip

v2: Squash in build fix (Alex)

Signed-off-by: Aric Cyr <aric.cyr@amd.com>
Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>