[XFS] Add compat handlers for data & rt growfs ioctls

The args for XFS_IOC_FSGROWFSDATA and XFS_IOC_FSGROWFSRTA
have padding on the end on intel, so add arg copyin functions,
and then just call the growfs ioctl helpers.

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>