airoha: Add initial support for Airoha AN7581 SoC

Add initial support for Airoha AN7581 SoC. This adds the initial Kconfig
and Makefile entry for the SoC, an U-Boot specific DTSI and initial config
for it. Also add the initial code for CPU and RAM initialization.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
diff --git a/arch/arm/mach-airoha/cpu.c b/arch/arm/mach-airoha/cpu.c
new file mode 100644
index 0000000..a578e96
--- /dev/null
+++ b/arch/arm/mach-airoha/cpu.c
@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <cpu_func.h>
+#include <dm.h>
+#include <init.h>
+#include <wdt.h>
+#include <dm/uclass-internal.h>
+
+int arch_cpu_init(void)
+{
+	icache_enable();
+
+	return 0;
+}
+
+void enable_caches(void)
+{
+	/* Enable D-cache. I-cache is already enabled in start.S */
+	dcache_enable();
+}