FROMGIT: f2fs: fix wrong continue condition in GC

We should decrease the frozen counter.

Cc: stable@vger.kernel.org
Fixes: 325163e9 ("f2fs: add gc_urgent_high_remaining sysfs node")
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
(cherry picked from commit 605b0a77
     https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git dev)
Change-Id: I892f215e778f7d89b9bbf3dfb292ed820944cf6b