drm/omap: fix tiled buffer stride calculations

omap_gem uses page alignment for buffer stride. The related calculations
are a bit off, though, as byte stride of 4096 gets aligned to 8192,
instead of 4096.

This patch changes the code to use DIV_ROUND_UP(), which fixes those
calculations and makes them more readable.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

drivers/gpu/drm/omapdrm/omap_gem.c

@@ -182,7 +182,7 @@ static void evict_entry(struct drm_gem_object *obj,
 	size_t size = PAGE_SIZE * n;
 	loff_t off = mmap_offset(obj) +
 			(entry->obj_pgoff << PAGE_SHIFT);
-	const int m = 1 + ((omap_obj->width << fmt) / PAGE_SIZE);
+	const int m = DIV_ROUND_UP(omap_obj->width << fmt, PAGE_SIZE);
 
 	if (m > 1) {
 		int i;
@@ -424,7 +424,7 @@ static int fault_2d(struct drm_gem_object *obj,
 	 * into account in some of the math, so figure out virtual stride
 	 * in pages
 	 */
-	const int m = 1 + ((omap_obj->width << fmt) / PAGE_SIZE);
+	const int m = DIV_ROUND_UP(omap_obj->width << fmt, PAGE_SIZE);
 
 	/* We don't use vmf->pgoff since that has the fake offset: */
 	pgoff = (vmf->address - vma->vm_start) >> PAGE_SHIFT;