[XFS] stop updating inode->i_blocks

The VFS doesn't use i_blocks, it's only used by generic_fillattr and the
generic quota code which XFS doesn't use. In XFS there is one use to check
whether we have an inline or out of line sumlink, but we can replace that
with a check of the XFS_IFINLINE inode flag.

SGI-PV: 971186
SGI-Modid: xfs-linux-melb:xfs-kern:30391a

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