MIPS: 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>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/17333/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/mm/dma-default.c

@@ -179,7 +179,7 @@ static int mips_dma_mmap(struct device *dev, struct vm_area_struct *vma,
 	void *cpu_addr, dma_addr_t dma_addr, size_t size,
 	unsigned long attrs)
 {
-	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 addr = (unsigned long)cpu_addr;
 	unsigned long off = vma->vm_pgoff;