packet: minor: remove unused err assignment

This tiny patch removes two unused err assignments. In those two cases the
err variable is either overwritten with another value at a later point in
time without having read the previous assigment, or it is assigned and the
function returns without using/reading err after the assignment.

Signed-off-by: Daniel Borkmann <daniel.borkmann@tik.ee.ethz.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>