[][mt7988][cpu][Add cache hierarchy device tree node]

[Description]
Add CPU cache hierarchy node to device tree. This prevents the kernel
from displaying the following warning message during boot-up:

"cacheinfo: Unable to detect cache hierarchy for CPU 0"

This warning message usually causes users to misunderstand that the
CPU cache is broken, when in reality it is caused by bus hanging.

[Release-log]
N/A


Change-Id: I0afbad319f658c8cb8e3a677a29f464abe51ba6c

Change-Id: Ie78266d1816bd994a21b5a2788a398c46463c427
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7421669
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 bae7604..c9da613 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
@@ -26,6 +26,7 @@
 			device_type = "cpu";
 			compatible = "arm,cortex-a73";
 			enable-method = "psci";
+			next-level-cache = <&l2_cache>;
 			reg = <0x0>;
 			clocks = <&mcusys CK_MCU_ARM_DIV_SEL>,
 				 <&topckgen CK_TOP_CB_NET1_D4>,
@@ -43,6 +44,7 @@
 			device_type = "cpu";
 			compatible = "arm,cortex-a73";
 			enable-method = "psci";
+			next-level-cache = <&l2_cache>;
 			reg = <0x1>;
 			clocks = <&mcusys CK_MCU_ARM_DIV_SEL>,
 				 <&topckgen CK_TOP_CB_NET1_D4>,
@@ -60,6 +62,7 @@
 			device_type = "cpu";
 			compatible = "arm,cortex-a73";
 			enable-method = "psci";
+			next-level-cache = <&l2_cache>;
 			reg = <0x2>;
 			clocks = <&mcusys CK_MCU_ARM_DIV_SEL>,
 				 <&topckgen CK_TOP_CB_NET1_D4>,
@@ -77,6 +80,7 @@
 			device_type = "cpu";
 			compatible = "arm,cortex-a73";
 			enable-method = "psci";
+			next-level-cache = <&l2_cache>;
 			reg = <0x3>;
 			clocks = <&mcusys CK_MCU_ARM_DIV_SEL>,
 				 <&topckgen CK_TOP_CB_NET1_D4>,
@@ -90,6 +94,11 @@
 			nvmem-cell-names = "calibration-data";
 		};
 
+		l2_cache: l2-cache {
+			compatible = "cache";
+			cache-level = <2>;
+		};
+
 		cluster0_opp: opp_table0 {
 			compatible = "operating-points-v2";
 			opp-shared;