drm/amd/display: Add debug option for idle optimizations on cursor updates

For optimizations and debug purposes we added an option to exit idle
operations on cursor updates.

Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alvin Lee <Alvin.Lee2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>