drm/imx: merge imx-drm-core and ipuv3-crtc in one module

While it is possible to hook other CRTC implementations into imx-drm
in practice there are none yet and the option to disable ipuv3-crtc
support has been hidden for a long time.

Now that the imx-drm-core has learned to deal with some of the
specifics of IPUv3 there is a cyclic dependency between both parts.
To get rid of this and to decimate the Kconfig maze a bit, simply
merge both parts into one module.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
diff --git a/drivers/gpu/drm/imx/imx-drm.h b/drivers/gpu/drm/imx/imx-drm.h
index 295434b..f6dd64b 100644
--- a/drivers/gpu/drm/imx/imx-drm.h
+++ b/drivers/gpu/drm/imx/imx-drm.h
@@ -29,6 +29,8 @@ int imx_drm_init_drm(struct platform_device *pdev,
 		int preferred_bpp);
 int imx_drm_exit_drm(void);
 
+extern struct platform_driver ipu_drm_driver;
+
 void imx_drm_mode_config_init(struct drm_device *drm);
 
 struct drm_gem_cma_object *imx_drm_fb_get_obj(struct drm_framebuffer *fb);