fs: add generic UNRESVSP and ZERO_RANGE ioctl handlers

These use the same scheme as the pre-existing mapping of the XFS
RESVP ioctls to ->falloc, so just extend it and remove the XFS
implementation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
[darrick: fix compile error on s390]
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_ioctl.h

@@ -9,7 +9,6 @@
 extern int
 xfs_ioc_space(
 	struct file		*filp,
-	unsigned int		cmd,
 	xfs_flock64_t		*bf);
 
 int