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

Try to mitigate potential future driver core api changes by adding a
padding to struct hd_struct, struct blk_integrity, and struct gendisk.

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

Bug: 151154716
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I5d19bf942fbedc64f705f5d27ae629c57209df27