[][SBC][MT7988][Add reserved memory for BL32]

[Description]
Add reserved memory for BL32, align reserved memory size
for SRAM from ATF, (TZRAM_SIZE + TZRAM2_SIZE) =
0x40000(BL31) + 0x10000(BL32) = 0x50000

[Release-log]
N/A

Change-Id: Icc6bb0af2d712fdcb835bcfec90b8902392c6482
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7272375
diff --git a/target/linux/mediatek/files-5.4/arch/arm64/boot/dts/mediatek/mt7988.dtsi b/target/linux/mediatek/files-5.4/arch/arm64/boot/dts/mediatek/mt7988.dtsi
index 1f881ea..364deef 100644
--- a/target/linux/mediatek/files-5.4/arch/arm64/boot/dts/mediatek/mt7988.dtsi
+++ b/target/linux/mediatek/files-5.4/arch/arm64/boot/dts/mediatek/mt7988.dtsi
@@ -294,9 +294,9 @@
 			pmsg-size = <0x2000>;
 		};
 
-		/* 256 KiB reserved for ARM Trusted Firmware (BL31) */
+		/* 320 KiB reserved for ARM Trusted Firmware (BL31 + BL32) */
 		secmon_reserved: secmon@43000000 {
-			reg = <0 0x43000000 0 0x40000>;
+			reg = <0 0x43000000 0 0x50000>;
 			no-map;
 		};