mm: use vma_is_anonymous() in create_huge_pmd() and wp_huge_pmd()

mm: use vma_is_anonymous() in create_huge_pmd() and wp_huge_pmd()

Let's use helper rather than direct check of vma->vm_ops to distinguish
anonymous VMA.

Signed-off-by: Kirill A. Shutemov <[email protected]>
Reviewed-by: Oleg Nesterov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>