[NET]: Remove unused "mibalign" argument for snmp_mib_init().

With fixes from Arnaldo Carvalho de Melo.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>