drm/amdgpu: refine mes firmware loading

v1:
refine mes firmware loading

v2:
use dev_info instead of DRM_INFO

Signed-off-by: Yang Wang <kevinyang.wang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>