ANDROID: GKI: sock.h: add Android ABI padding to some structures

Try to mitigate potential future driver core api changes by adding a
padding to struct sock.

Based on a patch from Michal Marek <mmarek@suse.cz> from the SLES kernel

Bug: 151154716
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I61c3d6cf12c087345db71fc6d93ee6bd58969003