Revert "drm/amd/display: add global master update lock for DCN2"

This reverts commit 6c5be4ac.

This commit was accidentally promoted twice

Signed-off-by: David Francis <David.Francis@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>