BACKPORT: f2fs: give priority to select unpinned section for foreground GC

Previously, during foreground GC, if victims contain data of pinned file,
it will fail migration of the data, and meanwhile i_gc_failures of that
pinned file may increase, and when it exceeds threshold, GC will unpin
the file, result in breaking pinfile's semantics.

In order to mitigate such condition, let's record and skip section which
has pinned file's data and give priority to select unpinned one.

Bug: 279387798
Bug: 302252039
Signed-off-by: Chao Yu <chao.yu@oppo.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
(cherry picked from commit bf123c9d)
[drosen: Resolved trivial conflict in fs/f2fs/gc.c ]
Change-Id: Id18929506ff9ecadd48ae48f6734205a65af0bd8
Signed-off-by: chenxin <chenxinxin@xiaomi.corp-partner.google.com>