f2fs: drop page cache after fs shutdown

Don't remain dirtied page cache in f2fs after shutdown, it can mitigate
memory pressure of whole system, in order to keep other modules working
properly.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
3 files changed