f2fs: compress: fix to relocate check condition in f2fs_ioc_{,de}compress_file()

f2fs: compress: fix to relocate check condition in f2fs_ioc_{,de}compress_file()

Compress flag should be checked after inode lock held to avoid
racing w/ f2fs_setflags_common() , fix it.

Fixes: 5fdb322ff2c2 ("f2fs: add F2FS_IOC_DECOMPRESS_FILE and F2FS_IOC_COMPRESS_FILE")
Reported-by: Zhiguo Niu <zhiguo.niu@unisoc.com>
Closes: https://lore.kernel.org/linux-f2fs-devel/CAHJ8P3LdZXLc2rqeYjvymgYHr2+YLuJ0sLG9DdsJZmwO7deuhw@mail.gmail.com
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>