xfs: remove xfs_iput

xfs_iput is just a small wrapper for xfs_iunlock + IRELE.  Having this
out of line wrapper means the trace events in those two can't track
their caller properly.  So just remove the wrapper and opencode the
unlock + rele in the few callers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>