f2fs: fix to handle F2FS_IOC_START_ATOMIC_REPLACE in f2fs_compat_ioctl()

Otherwise, 32-bits binary call ioctl(F2FS_IOC_START_ATOMIC_REPLACE) will
fail in 64-bits kernel.

Fixes: 41e8f85a

 ("f2fs: introduce F2FS_IOC_START_ATOMIC_REPLACE")
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>