Use vma_pages function on vma object instead of explicit computation. This is a clean up patch.A version of this is already queued for -next here: https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/commit/?h=for-next/core&id=b4f4a2755665bf847231050b569f587ce0945482
Ah. Please ignore the patch. Thanks.
