[NETROM]: Fix locking order when establishing a NETROM circuit.

When establishing a new circuit in nr_rx_frame the locks are taken in
a different order than in the rest of the stack.  This should be
harmless but triggers lockdep.  Either way, reordering the code a
little solves the issue.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: David S. Miller <davem@davemloft.net>