[XFS] xfs_setattr currently doesn't just handle the attributes set through

->setattr but also addition XFS-specific attributes: project id, inode
flags and extent size hint. Having these in a single function makes it
more complicated and forces to have us a bhv_vattr intermediate structure
eating up stackspace.

This patch adds a new xfs_ioctl_setattr helper for the XFS ioctls that set
these attributes and remove the code to set them through xfs_setattr.

SGI-PV: 984564

SGI-Modid: xfs-linux-melb:xfs-kern:31677a

Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Tim Shimmin <tes@sgi.com>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>