drm/exynos: fix layering violation of address

There is no guarantee that DMA addresses are the same as physical
addresses, but dma_to_pfn() knows how to convert a dma_addr_t to a PFN
which can then be converted to a struct page.
Suggested-by: NRussell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: NJoonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: NInki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_gem.c

@@ -77,7 +77,8 @@ static int exynos_drm_alloc_buf(struct exynos_drm_gem_obj *obj)
 
 		start_addr = obj->dma_addr;
 		while (i < nr_pages) {
-			obj->pages[i] = phys_to_page(start_addr);
+			obj->pages[i] = pfn_to_page(dma_to_pfn(dev->dev,
+							       start_addr));
 			start_addr += PAGE_SIZE;
 			i++;
 		}