KVM: PPC: BookE: Use vma_pages function

Use vma_pages function on vma object instead of explicit computation.
Found by coccinelle spatch "api/vma_pages.cocci"
Signed-off-by: NThomas Meyer <thomas@m3y3r.de>
Signed-off-by: NPaul Mackerras <paulus@ozlabs.org>

arch/powerpc/kvm/e500_mmu_host.c

@@ -377,7 +377,7 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
 
 			start = vma->vm_pgoff;
 			end = start +
-			      ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT);
+			      vma_pages(vma);
 
 			pfn = start + ((hva - vma->vm_start) >> PAGE_SHIFT);