drm/komeda: plane: switch to plane reset helper

komeda_plane_reset() does the state initialisation by copying a lot of
the code found in the __drm_atomic_helper_plane_reset(). Let's switch to
that helper and reduce the boilerplate.

Cc: Brian Starkey <brian.starkey@arm.com>
Cc: "James (Qian) Wang" <james.qian.wang@arm.com>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Mihail Atanassov <mihail.atanassov@arm.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220221095918.18763-2-maxime@cerno.tech

drivers/gpu/drm/arm/display/komeda/komeda_plane.c

@@ -145,14 +145,10 @@ static void komeda_plane_reset(struct drm_plane *plane)
 
 	state = kzalloc(sizeof(*state), GFP_KERNEL);
 	if (state) {
-		state->base.rotation = DRM_MODE_ROTATE_0;
-		state->base.pixel_blend_mode = DRM_MODE_BLEND_PREMULTI;
-		state->base.alpha = DRM_BLEND_ALPHA_OPAQUE;
+		__drm_atomic_helper_plane_reset(plane, &state->base);
 		state->base.zpos = kplane->layer->base.id;
 		state->base.color_encoding = DRM_COLOR_YCBCR_BT601;
 		state->base.color_range = DRM_COLOR_YCBCR_LIMITED_RANGE;
-		plane->state = &state->base;
-		plane->state->plane = plane;
 	}
 }