xfs: clean up sign warnings in dir2 code

We are now consistently using unsigned char strings for names
so fix up the remaining warnings in the dir2 code to complete
the cleanup.

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

diff --cc fs/xfs/xfs_dir2.c
Simple merge

diff --cc fs/xfs/xfs_dir2_block.c
Simple merge

diff --cc fs/xfs/xfs_dir2_leaf.c
Simple merge

diff --cc fs/xfs/xfs_dir2_sf.c
Simple merge