riscv: board: Add nx25-ae250 to support RISC-V

Add nx25-ae250 board to do platform initializations.

Signed-off-by: Rick Chen <rick@andestech.com>
Signed-off-by: Rick Chen <rickchen36@gmail.com>
Signed-off-by: Greentime Hu <green.hu@gmail.com>
diff --git a/board/AndesTech/nx25-ae250/Kconfig b/board/AndesTech/nx25-ae250/Kconfig
new file mode 100644
index 0000000..2fb3234
--- /dev/null
+++ b/board/AndesTech/nx25-ae250/Kconfig
@@ -0,0 +1,24 @@
+if TARGET_NX25_AE250
+
+config SYS_CPU
+	default "nx25"
+
+config SYS_BOARD
+	default "nx25-ae250"
+
+config SYS_VENDOR
+	default "AndesTech"
+
+config SYS_SOC
+	default "ae250"
+
+config SYS_CONFIG_NAME
+	default "nx25-ae250"
+
+config ENV_SIZE
+	default 0x2000 if ENV_IS_IN_SPI_FLASH
+
+config ENV_OFFSET
+	default 0x140000 if ENV_IS_IN_SPI_FLASH
+
+endif