drm/mgag200: drop use of drmP.h

Drop use of the deprecated drmP.h header file.
Replace with necessary include files to fix build.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Link: https://patchwork.freedesktop.org/patch/msgid/20190623103542.30697-5-sam@ravnborg.org

drivers/gpu/drm/mgag200/mgag200_main.c

@@ -7,9 +7,11 @@
  *          Matt Turner
  *          Dave Airlie
  */
-#include <drm/drmP.h>
+
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_gem_framebuffer_helper.h>
+#include <drm/drm_pci.h>
+
 #include "mgag200_drv.h"
 
 static const struct drm_mode_config_funcs mga_mode_funcs = {