Fix remount races with symlink handling in affs

A couple of fields in affs_sb_info is used in follow_link() and
symlink() for handling AFFS "absolute" symlinks.  Need locking
against affs_remount() updates.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --cc fs/affs/affs.h
Simple merge

diff --cc fs/affs/namei.c
Simple merge

diff --cc fs/affs/super.c
Simple merge

diff --cc fs/affs/symlink.c
Simple merge