Revert "neighbour: fix unaligned access to pneigh_entry"

This reverts commit ab0eca3f which is
commit ed779fe4 upstream.

It breaks the Android kernel abi, so revert it for now.  If it is needed
in the future it can come back in an abi-safe way.

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