f2fs: replace test_and_set/clear_bit() with set/clear_bit()

Since set/clear_inode_flag() don't need to return value to show
if flag is set, we can just call set/clear_bit() here.

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