xfs: rename xfs_get_perag

xfs_get_perag is really getting the perag that an inode belongs to
based on it's inode number. Convert the use of this function to just
get the perag from a provided ag number.  Use this new function to
obtain the per-ag structure when traversing the per AG inode trees
for sync and reclaim.

Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

diff --cc fs/xfs/linux-2.6/xfs_sync.c
Simple merge

diff --cc fs/xfs/xfs_iget.c
Simple merge

diff --cc fs/xfs/xfs_inode.c
Simple merge

diff --cc fs/xfs/xfs_mount.h
Simple merge