ANDROID: GKI: sched: add Android ABI padding to some structures

Try to mitigate potential future driver core api changes by adding a
padding to struct user_struct and struct sched_domain.

Based on a change made to the RHEL/CENTOS 8 kernel.

Bug: 151154716
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ie8f685122767b690a116193aefd8c5e3b6ef8f17