f2fs: clear PageError on writepage

Cherry-pick from origin/upstream-f2fs-stable-linux-4.9.y:
commit 926b3701 ("f2fs: clear PageError on writepage")

This patch clears PageError in some pages tagged by read path, but when we
write the pages with valid contents, writepage should clear the bit likewise
ext4.

Change-Id: I01ec79dc5e209c44b4b5e0de69459eb8c32b1a95
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>