[XFS] Fix compat XFS_IOC_FSBULKSTAT_SINGLE ioctl

The XFS_IOC_FSBULKSTAT_SINGLE ioctl passes in the
desired inode number, while XFS_IOC_FSBULKSTAT passes
in the previous/last-stat'd inode number.  The
compat handler wasn't differentiating these, so
when a XFS_IOC_FSBULKSTAT_SINGLE request for inode
128 was sent in, stat information for 131 was sent out.

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