btrfs: Show device attr correctly for symlinks
Symlinks and files of other types show different device numbers, though
they are on the same partition:
$ touch tmp; ln -s tmp tmp2; stat tmp tmp2
File: `tmp'
Size: 0 Blocks: 0 IO Block: 4096 regular empty file
Device: 15h/21d Inode: 984027 Links: 1
--- snip ---
File: `tmp2' -> `tmp'
Size: 3 Blocks: 0 IO Block: 4096 symbolic link
Device: 13h/19d Inode: 984028 Links: 1
Reported-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>