fs: Add new pre-allocation ioctls to vfs for compatibility with legacy xfs ioctls

fs: Add new pre-allocation ioctls to vfs for compatibility with legacy xfs ioctls

This patch adds ioctls to vfs for compatibility with legacy XFS
pre-allocation ioctls (XFS_IOC_*RESVP*). The implementation
effectively invokes sys_fallocate for the new ioctls.
Also handles the compat_ioctl case.
Note: These legacy ioctls are also implemented by OCFS2.

[AV: folded fixes from hch]

Signed-off-by: Ankit Jain <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: Al Viro <[email protected]>