drm/meson: drop use of drmP.h

Drop use of the deprecated drmP.h header.
While doing so used the opportunity
to clean up a little so includes are now
sorted and removed unused include files.
In a few cases added some forwards to allow header
files to built in different include order.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Maxime Jourdan <mjourdan@baylibre.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: linux-amlogic@lists.infradead.org
Cc: linux-arm-kernel@lists.infradead.org
Link: https://patchwork.freedesktop.org/patch/msgid/20190716064220.18157-2-sam@ravnborg.org

drivers/gpu/drm/meson/meson_drv.h

@@ -7,11 +7,14 @@
 #ifndef __MESON_DRV_H
 #define __MESON_DRV_H
 
-#include <linux/platform_device.h>
-#include <linux/regmap.h>
+#include <linux/device.h>
 #include <linux/of.h>
-#include <linux/soc/amlogic/meson-canvas.h>
-#include <drm/drmP.h>
+#include <linux/regmap.h>
+
+struct drm_crtc;
+struct drm_device;
+struct drm_plane;
+struct meson_drm;
 
 struct meson_drm {
 	struct device *dev;