drm/drm_pci.c: Use dma_zalloc_coherent

Replace dma_alloc_coherent + memset with dma_zalloc_coherent.
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20181023040222.GA1540@jordon-HP-15-Notebook-PC

drivers/gpu/drm/drm_pci.c

@@ -61,15 +61,14 @@ drm_dma_handle_t *drm_pci_alloc(struct drm_device * dev, size_t size, size_t ali
 		return NULL;
 
 	dmah->size = size;
-	dmah->vaddr = dma_alloc_coherent(&dev->pdev->dev, size, &dmah->busaddr, GFP_KERNEL | __GFP_COMP);
+	dmah->vaddr = dma_zalloc_coherent(&dev->pdev->dev, size, &dmah->busaddr,
+						GFP_KERNEL | __GFP_COMP);
 
 	if (dmah->vaddr == NULL) {
 		kfree(dmah);
 		return NULL;
 	}
 
-	memset(dmah->vaddr, 0, size);
-
 	/* XXX - Is virt_to_page() legal for consistent mem? */
 	/* Reserve */
 	for (addr = (unsigned long)dmah->vaddr, sz = size;