tee: amdtee: print error message if tee not present

If there is no TEE with which the driver can communicate, then
print an error message and return.

Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Rijo Thomas <Rijo-john.Thomas@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>