f2fs: avoid stat_inc_atomic_write for non-atomic file

After filemap_write_and_wait_range fail, the FI_ATOMIC_FILE flags is removed,
so that f2fs should not increase the stat of atomic_write.

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>