f2fs: remove redundant atomic file check in defragment

f2fs_is_atomic_file(inode) is checked in f2fs_defragment_range,
so remove the redundant checking in f2fs_ioc_defragment.

Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>