microblaze: Cocci spatch "vma_pages"

Use vma_pages function on vma object instead of explicit computation.
Found by coccinelle spatch "api/vma_pages.cocci"
Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/microblaze/kernel/dma.c

@@ -165,7 +165,7 @@ int dma_direct_mmap_coherent(struct device *dev, struct vm_area_struct *vma,
 			     unsigned long attrs)
 {
 #ifdef CONFIG_MMU
-	unsigned long user_count = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
+	unsigned long user_count = vma_pages(vma);
 	unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
 	unsigned long off = vma->vm_pgoff;
 	unsigned long pfn;