drm/amd/display: Change locking of registers when flipping frames.

- Introduce GRPH_UPDATE_LOCK around programming surface flip.
- Remove the now unused graphic surface lock.
- Add macros to get and set four registers
- both immediate and H Retrace should not be enabled at the same time

Signed-off-by: Andrew Wong <andrew.wong1@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>