f2fs: Revert "f2fs: Fix indefinite loop in f2fs_gc() v1"

f2fs: Revert "f2fs: Fix indefinite loop in f2fs_gc() v1"

This reverts commit 615bb0604031d824f754cfd25955b558bf08367d.

The patch "f2fs: Fix indefinite loop in f2fs_gc()" v1 and v4 are all
merged. Patch v4 is test info for patch v1. Patch v1 doesn't work and
may cause that sbi->cur_victim_sec can't be resetted to NULL_SEGNO,
which makes SSR unable to get segment of sbi->cur_victim_sec.
So it should be reverted.

The mails record:
[1] https://lore.kernel.org/linux-f2fs-devel/7288dcd4-b168-7656-d1af-7e2cafa4f720@huawei.com/T/
[2] https://lore.kernel.org/linux-f2fs-devel/20190809153653.GD93481@jaegeuk-macbookpro.roam.corp.google.com/T/

Signed-off-by: Jia Yang <jiayang5@huawei.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>