drm/i915/fbdev: Implement fb_dirty for intel custom fb helper

After disconnecting damage worker from update logic it's left to fbdev
emulation implementation to have fb_dirty function. Currently intel
fbdev doesn't have it. This is causing problems to features (PSR, FBC,
DRRS) relying on dirty callback.

Implement simple fb_dirty callback to deliver notifications about updates
in fb console.

v4: Add proper Fixes tag and modify commit message
v3: Check damage clip
v2: Improved commit message and added Fixes tag

Fixes: f231af49 ("drm/fb-helper: Disconnect damage worker from update logic")
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230123074437.475103-1-jouni.hogander@intel.com

drivers/gpu/drm/i915/display/intel_fbdev.c

@@ -321,8 +321,20 @@ static int intelfb_create(struct drm_fb_helper *helper,
 	return ret;
 }
 
+static int intelfb_dirty(struct drm_fb_helper *helper, struct drm_clip_rect *clip)
+{
+	if (!(clip->x1 < clip->x2 && clip->y1 < clip->y2))
+		return 0;
+
+	if (helper->fb->funcs->dirty)
+		return helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, clip, 1);
+
+	return 0;
+}
+
 static const struct drm_fb_helper_funcs intel_fb_helper_funcs = {
 	.fb_probe = intelfb_create,
+	.fb_dirty = intelfb_dirty,
 };
 
 static void intel_fbdev_destroy(struct intel_fbdev *ifbdev)