n2_crypto: Attach on Niagara-T3.

A small modification was necessary since in the machine description
for 'n2cp' and 'ncp' nodes, there no longer is an 'intr' property.

That's OK because this property was always nothing more than an
array of integers '1' ... 'nr_inos + 1' so we can just compute it
in-place.

Signed-off-by: David S. Miller <davem@davemloft.net>