net: core: fix for ipv6 neigh

Attach proper timer function with ipv6 neighbour entry.
Since proper timer function was not attached
to neighbour entry kernel was deleting the
neigbour entry without sending the neighbour probe.

Change-Id: Ifafcc3c4ddecc26c6ca83d5843400d0be4169566
Acked-by: Suraj Jaiswal <c_surajj@qti.qualcomm.com>
Signed-off-by: Mohammed Javid <mjavid@codeaurora.org>