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/Kconfig b/arch/arm/mach-airoha/Kconfig
new file mode 100644
index 0000000..be3562a
--- /dev/null
+++ b/arch/arm/mach-airoha/Kconfig
@@ -0,0 +1,32 @@
+if ARCH_AIROHA
+
+config SYS_VENDOR
+	default "airoha"
+
+choice
+	prompt "Airoha board select"
+
+config TARGET_AN7581
+	bool "Airoha AN7581 SoC"
+	select ARM64
+	help
+	  The Airoha EN7581 is a ARM-based SoC with a quad-core Cortex-A7
+	  including NEON and GPU, Mali-450 graphics, several DDR3 options,
+	  crypto engine, built-in Wi-Fi / Bluetooth combo chip, JPEG decoder,
+	  video interfaces supporting HDMI and MIPI, and video codec support.
+	  Peripherals include Gigabit Ethernet, switch, USB3.0 and OTG, PCIe,
+	  I2S, PCM, S/PDIF, UART, SPI, I2C, IR TX/RX, and PWM.
+
+endchoice
+
+config SYS_SOC
+	default "an7581" if TARGET_AN7581
+
+config SYS_BOARD
+	default "an7581" if TARGET_AN7581
+
+config SYS_CONFIG_NAME
+	default "an7581" if TARGET_AN7581
+
+endif
+