xfs: remove XFS_IOC_FSSETDM and XFS_IOC_FSSETDM_BY_HANDLE

Thes ioctls set DMAPI specific flags in the on-disk inode, but there is
no way to actually ever query those flags.  The only known user is
xfsrestore with the -D option, which is documented to be only useful
inside a DMAPI enviroment, which isn't supported by upstream XFS.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>