xfs: remove if_rdev

xfs: remove if_rdev

Source kernel commit: 66f364649d870c7541c30a2f02a32fd4c88684f0

We can simply use the i_rdev field in the Linux inode and just convert
to and from the XFS dev_t when reading or logging/writing the inode.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
[sandeen: add i_rdev to our mocked up inode in userspace]
[djwong: use IRIX_DEV macros, assign in i_rdev in libxfs_ialloc]
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>