drm/amd/display: Implement INBOX0 usage in driver

[Why]
Start using INBOX0 for HW Lock command

[How]
- Implement initial interface for INBOX0 HW lock message

Signed-off-by: Alvin Lee <Alvin.Lee2@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>