More kernfs_open_file->mutex synchronized flags are planned to be
added.  Convert ->mmapped to a bitfield in preparation.
While at it, make kernfs_fop_mmap() use "true" instead of "1" on
->mmapped.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Acked-by: Zefan Li <lizefan@huawei.com>
                goto out_put;
 
        rc = 0;
-       of->mmapped = 1;
+       of->mmapped = true;
        of->vm_ops = vma->vm_ops;
        vma->vm_ops = &kernfs_vm_ops;
 out_put:
 
        char                    *prealloc_buf;
 
        size_t                  atomic_write_len;
-       bool                    mmapped;
+       bool                    mmapped:1;
        const struct vm_operations_struct *vm_ops;
 };