Merge latest F2FS driver updates for 3.4.y branch.

all change logs can be found here: thanks @Alucard for merging.

https://github.com/Alucard24/Alucard-Kernel-jfltexx/commits/my-aospv2-4.4/fs/f2fs
workqueue: change BUG_ON() to WARN_ON()

This BUG_ON() can be triggered if you call schedule_work() before
calling INIT_WORK().  It is a bug definitely, but it's nicer to just
print a stack trace and return.

Reported-by: Matt Renzelmann <mjr@cs.wisc.edu>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Tejun Heo <tj@kernel.org>