f2fs: clear FI_HOT_DATA correctly

This patch fixes to clear FI_HOT_DATA correctly in below path:
- error handling in f2fs_ioc_start_atomic_write
- after commit atomic write in f2fs_ioc_commit_atomic_write
- after drop atomic write in drop_inmem_pages

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