compat_ioctl: block: handle BLKGETZONESZ/BLKGETNRZONES

These were added to blkdev_ioctl() in v4.20 but not blkdev_compat_ioctl,
so add them now.

Cc: <stable@vger.kernel.org> # v4.20+
Fixes: 72cd8757 ("block: Introduce BLKGETZONESZ ioctl")
Fixes: 65e4e3ee

 ("block: Introduce BLKGETNRZONES ioctl")
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>