drm: avoid includes in drm_crtc_helper_internal.h

Prefer forward declarations over includes where possible.
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/fb7fb2986e19f949bf3a9b16230a59e0f7aaebdf.1709898638.git.jani.nikula@intel.com

drivers/gpu/drm/drm_crtc_helper_internal.h

@@ -29,10 +29,12 @@
 #ifndef __DRM_CRTC_HELPER_INTERNAL_H__
 #define __DRM_CRTC_HELPER_INTERNAL_H__
 
-#include <drm/drm_connector.h>
-#include <drm/drm_crtc.h>
-#include <drm/drm_encoder.h>
-#include <drm/drm_modes.h>
+enum drm_mode_status;
+struct drm_connector;
+struct drm_crtc;
+struct drm_display_mode;
+struct drm_encoder;
+struct drm_modeset_acquire_ctx;
 
 /* drm_probe_helper.c */
 enum drm_mode_status drm_crtc_mode_valid(struct drm_crtc *crtc,