drm/komeda: Creates plane alpha and blend mode properties

Creates plane alpha and blend mode properties attached to plane.

This patch depends on:
- https://patchwork.freedesktop.org/series/59915/
- https://patchwork.freedesktop.org/series/58665/
- https://patchwork.freedesktop.org/series/59000/
- https://patchwork.freedesktop.org/series/59002/
- https://patchwork.freedesktop.org/series/59471/

Changes since v1:
- Adds patch denpendency in the comment

Changes since v2:
- Remove [RFC] from the subject

Changes since v3:
- Rebase the code
Signed-off-by: Lowry Li (Arm Technology China) <lowry.li@arm.com>
Reviewed-by: James Qian Wang (Arm Technology China) <james.qian.wang@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>

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

@@ -301,6 +301,17 @@ static int komeda_plane_add(struct komeda_kms_dev *kms,
 
 	drm_plane_helper_add(plane, &komeda_plane_helper_funcs);
 
+	err = drm_plane_create_alpha_property(plane);
+	if (err)
+		goto cleanup;
+
+	err = drm_plane_create_blend_mode_property(plane,
+			BIT(DRM_MODE_BLEND_PIXEL_NONE) |
+			BIT(DRM_MODE_BLEND_PREMULTI)   |
+			BIT(DRM_MODE_BLEND_COVERAGE));
+	if (err)
+		goto cleanup;
+
 	err = komeda_plane_create_layer_properties(kplane, layer);
 	if (err)
 		goto cleanup;