xfs: move xfs_fsb_to_db to xfs_bmap.h

This is the only remaining useful function in xfs_rw.h, so move it
to a header file responsible for block mapping functions that the
callers already include. Soon we can get rid of xfs_rw.h.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_bmap.h

@@ -211,6 +211,9 @@ int	xfs_bmap_count_blocks(struct xfs_trans *tp, struct xfs_inode *ip,
 		int whichfork, int *count);
 int	xfs_bmap_punch_delalloc_range(struct xfs_inode *ip,
 		xfs_fileoff_t start_fsb, xfs_fileoff_t length);
+
+xfs_daddr_t xfs_fsb_to_db(struct xfs_inode *ip, xfs_fsblock_t fsb);
+
 #endif	/* __KERNEL__ */
 
 #endif	/* __XFS_BMAP_H__ */