drm/amdgpu: Add more checks to PSP mailbox

Instead of checking the response flag, use status mask also to check
against any unexpected failures like a device drop. Also, log error if
waiting on a psp response fails/times out.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>