drm/gma500: make local header files more self-contained

Add proper forward declarations to minimize dependencies on
other header files.

Just add enough that we can safely include all header files in
alphabetically order in relevant files.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190519195526.3422-4-sam@ravnborg.org

drivers/gpu/drm/gma500/blitter.h

@@ -17,6 +17,8 @@
 #ifndef __BLITTER_H
 #define __BLITTER_H
 
+struct drm_psb_private;
+
 extern int gma_blt_wait_idle(struct drm_psb_private *dev_priv);
 
 #endif

drivers/gpu/drm/gma500/cdv_device.h

@@ -15,6 +15,10 @@
  * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+struct drm_crtc;
+struct drm_device;
+struct psb_intel_mode_device;
+
 extern const struct drm_crtc_helper_funcs cdv_intel_helper_funcs;
 extern const struct drm_crtc_funcs cdv_intel_crtc_funcs;
 extern const struct gma_clock_funcs cdv_clock_funcs;

drivers/gpu/drm/gma500/gma_device.h

@@ -15,6 +15,7 @@
 
 #ifndef _GMA_DEVICE_H
 #define _GMA_DEVICE_H
+struct drm_device;
 
 extern void gma_get_core_freq(struct drm_device *dev);
 

drivers/gpu/drm/gma500/gma_display.h

@@ -24,6 +24,9 @@
 
 #include <linux/pm_runtime.h>
 
+struct drm_encoder;
+struct drm_mode_set;
+
 struct gma_clock_t {
 	/* given values */
 	int n;

drivers/gpu/drm/gma500/mid_bios.h

@@ -16,6 +16,7 @@
  * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
  *
  **************************************************************************/
+struct drm_device;
 
 extern int mid_chip_setup(struct drm_device *dev);
 

drivers/gpu/drm/gma500/oaktrail.h

@@ -17,6 +17,8 @@
  *
  **************************************************************************/
 
+struct psb_intel_mode_device;
+
 /* MID device specific descriptors */
 
 struct oaktrail_timing_info {