btrfs: cleanup noused initialization of dev in btrfs_end_bio()
btrfs: cleanup noused initialization of dev in btrfs_end_bio()

It is introduced by:
 c404e0dc2c843b154f9a36c3aec10d0a715d88eb
 Btrfs: fix use-after-free in the finishing procedure of the device replace

But seems no relationship with that bug, this patch revirt these
code block for cleanup.

Signed-off-by: Zhao Lei <aacdd228f50c574b28b524b23f12fb9d52d6e0e3@cn.fujitsu.com>
Signed-off-by: Chris Mason <e2e8c5702d8ed5f565988a1cf5bb35c9ce199e5e@fb.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs