drm/amdgpu:invoke new implemented AI MB func

Implement the sr-iov mailbox for soc15 asics.

Signed-off-by: Monk Liu <Monk.Liu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>