net: core: Fix to update the neigh entry correctly

When neigh_probe_enable is enabled, neigh entry is not updated
when the client updates the mac address. Make a change to update
the neigh entry always.

Change-Id: I5bee340435b61e97186b99bc76ea9f1f0f3bf2e2
Acked-by: Chaitanya Pratapa <cpratapa@qti.qualcomm.com>
Signed-off-by: Mohammed Javid <mjavid@codeaurora.org>