drm/msm: add helper to allocate stolen fb

We'll later want to re-use this for state-readback when bootloader
enables display, so that we can create an fb for the initial
plane->state->fb.

Signed-off-by: Rob Clark <robdclark@gmail.com>
diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
index 1b627f2..db137f3 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -256,6 +256,8 @@ struct drm_framebuffer *msm_framebuffer_init(struct drm_device *dev,
 		const struct drm_mode_fb_cmd2 *mode_cmd, struct drm_gem_object **bos);
 struct drm_framebuffer *msm_framebuffer_create(struct drm_device *dev,
 		struct drm_file *file, const struct drm_mode_fb_cmd2 *mode_cmd);
+struct drm_framebuffer * msm_alloc_stolen_fb(struct drm_device *dev,
+		int w, int h, int p, uint32_t format);
 
 struct drm_fb_helper *msm_fbdev_init(struct drm_device *dev);
 void msm_fbdev_free(struct drm_device *dev);