net: netcp: check for interface handle in netcp_module_probe()

Currently netcp_module_probe() doesn't check the return value of
of_parse_phandle() that points to the interface data for the
module and then pass the node ptr to the module which is incorrect.
Check for return value and free the intf_modpriv if there is error.

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>