drm/exynos: added missed vm area region mapping type.

with this patch, if the memory region is physically non-continuous
then VM_MIXEDMAP is set to vm->vm_flags otherwise VM_PFNMAP.
we had missed this flag setting.

Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
diff --git a/drivers/gpu/drm/exynos/exynos_drm_gem.c b/drivers/gpu/drm/exynos/exynos_drm_gem.c
index f09d292..01139c8 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_gem.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_gem.c
@@ -514,6 +514,8 @@
 		if (!buffer->pages)
 			return -EINVAL;
 
+		vma->vm_flags |= VM_MIXEDMAP;
+
 		do {
 			ret = vm_insert_page(vma, uaddr, buffer->pages[i++]);
 			if (ret) {