drm/amdkfd: Add more error printing to help bringup v2

v2: Turned WARN into dev_warn and made the message more helpful

Signed-off-by: Yong Zhao <Yong.Zhao@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>