drm/amdgpu: change redundant init logs to debug level

When this VF stays in exclusive mode for long, other VFs will be
impacted.

The redundant messages causes exclusive mode timeout when they're
redirected. That is a normal use case for cloud service to redirect
guest log to virtual serial port.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: pding <Pixel.Ding@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>