f2fs: use generic names for generic ioctls

Don't define F2FS_IOC_* aliases to ioctls that already have a generic
FS_IOC_* name.  These aliases are unnecessary, and they make it unclear
which ioctls are f2fs-specific and which are generic.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>