f2fs: constify super_operations

commit f62fc9f97602d5f52fd574db80d95d71869bfe21 upstream.

super_operations are not supposed to change at runtime.
"struct super_block" working with super_operations provided
by <linux/fs.h> work with const super_operations. So mark
the non-const structs as const

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Git-commit: 72eceb89
Git-repo: https://android.googlesource.com/kernel/common.git


Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>