drm/selftests: Fix build warning -Wframe-larger-than

It seems for some random configuration drm_device is bigger than 2048
bytes.
The fix is to make the mock objects static variables.

Bug reported by 0-DAY Kernel test infrastructure here:
https://lists.01.org/pipermail/kbuild-all/2018-November/054431.html

Fixes: 6ff3d9ff ("drm/selftests: Add tests for drm_internal_framebuffer_create")
Signed-off-by: Alexandru-Cosmin Gheorghe <alexandru-cosmin.gheorghe@arm.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181102130103.7753-1-alexandru-cosmin.gheorghe@arm.com

drivers/gpu/drm/selftests/test-drm_framebuffer.c

@@ -307,14 +307,11 @@ static struct drm_framebuffer *fb_create_mock(struct drm_device *dev,
 	return ERR_PTR(-EINVAL);
 }
 
-static int execute_drm_mode_fb_cmd2(struct drm_mode_fb_cmd2 *r)
-{
-	int buffer_created = 0;
-	struct drm_framebuffer *fb;
-	struct drm_mode_config_funcs mock_config_funcs = {
+static struct drm_mode_config_funcs mock_config_funcs = {
 	.fb_create = fb_create_mock,
-	};
-	struct drm_device mock_drm_device = {
+};
+
+static struct drm_device mock_drm_device = {
 	.mode_config = {
 		.min_width = MIN_WIDTH,
 		.max_width = MAX_WIDTH,
@@ -323,9 +320,14 @@ static int execute_drm_mode_fb_cmd2(struct drm_mode_fb_cmd2 *r)
 		.allow_fb_modifiers = true,
 		.funcs = &mock_config_funcs,
 	},
-		.dev_private = &buffer_created
-	};
+};
+
+static int execute_drm_mode_fb_cmd2(struct drm_mode_fb_cmd2 *r)
+{
+	int buffer_created = 0;
+	struct drm_framebuffer *fb;
 
+	mock_drm_device.dev_private = &buffer_created;
 	fb = drm_internal_framebuffer_create(&mock_drm_device, r, NULL);
 	return buffer_created;
 }