net: qrtr: Fix error pointer vs NULL bugs

The callers only expect NULL pointers, so returning an error pointer
will lead to an Oops.

Fixes: 0c2204a4

 ("net: qrtr: Migrate nameservice to kernel from userspace")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>