6lowpan: reassembly: fix return of init function

This patch adds a missing return after fragmentation init. Otherwise we
register a sysctl interface and deregister it afterwards which makes no
sense.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc net/ieee802154/reassembly.c
Simple merge