feat(mt8188): increase TZRAM_SIZE from 192KB to 256KB

Increase TZRAM_SIZE to 256KB for MT8188 APUSYS.

Change-Id: Iabe1a4aeb79ba23c3e963170a8eb9ce19f2925f3
diff --git a/plat/mediatek/mt8188/include/platform_def.h b/plat/mediatek/mt8188/include/platform_def.h
index fc9725e..73b0ed3 100644
--- a/plat/mediatek/mt8188/include/platform_def.h
+++ b/plat/mediatek/mt8188/include/platform_def.h
@@ -193,7 +193,7 @@
  * Platform memory map related constants
  ******************************************************************************/
 #define TZRAM_BASE			(0x54600000)
-#define TZRAM_SIZE			(0x00030000)
+#define TZRAM_SIZE			(0x00040000)
 
 /*******************************************************************************
  * BL31 specific defines.