drm/mediatek: ovl: Refine ignore_pixel_alpha comment and placement

Refine the comment for ignore_pixel_alpha flag and move it to
if(state->fb) statement to make it less conditional.

Signed-off-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20241009034646.13143-3-jason-jh.lin@mediatek.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

Author: Jason-JH.Lin

drivers/gpu/drm/mediatek/mtk_disp_ovl.c

@@ -481,16 +481,16 @@ void mtk_ovl_layer_config(struct device *dev, unsigned int idx,
 		 */
 		if (blend_mode || state->base.fb->format->has_alpha)
 			con |= OVL_CON_AEN;
-	}
 
-	/* CONST_BLD must be enabled for XRGB formats although the alpha channel
-	 * can be ignored, or OVL will still read the value from memory.
-	 * For RGB888 related formats, whether CONST_BLD is enabled or not won't
-	 * affect the result. Therefore we use !has_alpha as the condition.
-	 */
-	if ((state->base.fb && !state->base.fb->format->has_alpha) ||
-	    blend_mode == DRM_MODE_BLEND_PIXEL_NONE)
-		ignore_pixel_alpha = OVL_CONST_BLEND;
+		/*
+		 * Although the alpha channel can be ignored, CONST_BLD must be enabled
+		 * for XRGB format, otherwise OVL will still read the value from memory.
+		 * For RGB888 related formats, whether CONST_BLD is enabled or not won't
+		 * affect the result. Therefore we use !has_alpha as the condition.
+		 */
+		if (blend_mode == DRM_MODE_BLEND_PIXEL_NONE || !state->base.fb->format->has_alpha)
+			ignore_pixel_alpha = OVL_CONST_BLEND;
+	}
 
 	if (pending->rotation & DRM_MODE_REFLECT_Y) {
 		con |= OVL_CON_VIRT_FLIP;