Revert "neighbour: fix unaligned access to pneigh_entry"

This reverts commit ab0eca3f.

It breaks the Android kernel abi, but will be brought in through a
different branch to ensure it ends up in the tree properly.

Bug: 161946584
Change-Id: I590afdcd9ea55980bab7dbc37bfa919a75c3a269
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>