drm/amd/display: Set static screen register for stoney/carrizo

-Set CRTC_STATIC_SCREEN_EVENT for stoney/carrizo for FBC implementation
-Code is currently guarded with "ENABLE_FBC" compile time flag

Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>