[XFS] remove some easy bhv_vnode_t instances

In various places we can just move a VFS_I call into the argument list of
called functions/macros instead of having a local bhv_vnode_t.

SGI-PV: 981498

SGI-Modid: xfs-linux-melb:xfs-kern:31776a

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