libfs: simple_follow_link()

let "fast" symlinks store the pointer to the body into ->i_link and
use simple_follow_link for ->follow_link()

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --cc fs/inode.c
Simple merge

diff --cc fs/libfs.c
Simple merge

diff --cc include/linux/fs.h
Simple merge