xfs: return a void pointer from xfs_buf_offset

This avoids all kinds of unessecary casts in an envrionment like Linux where
we can assume that pointer arithmetics are support on void pointers.

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

diff --cc fs/xfs/libxfs/xfs_ialloc.h
Simple merge

diff --cc fs/xfs/libxfs/xfs_inode_buf.c
Simple merge

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

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

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

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