drm/exynos: Fix potential NULL pointer dereference

Pointer was being dereferenced after freeing.

Fixes the following error:
drivers/gpu/drm/exynos/exynos_drm_g2d.c:323 g2d_userptr_put_dma_addr() error:
dereferencing freed memory 'g2d_userptr'

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
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_g2d.c b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
index c1054cb..6ffa076 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_g2d.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
@@ -319,8 +319,8 @@
 	g2d_userptr->sgt = NULL;
 
 	kfree(g2d_userptr->pages);
-	kfree(g2d_userptr);
 	g2d_userptr->pages = NULL;
+	kfree(g2d_userptr);
 	g2d_userptr = NULL;
 }