riscv: kconfig: Normalize architecture name spelling

It's RISC-V that is the official name, not RISCV.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Rick Chen <rick@andestech.com>
diff --git a/arch/Kconfig b/arch/Kconfig
index 9b4bcbf..49f0d44 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -60,7 +60,7 @@
 	select SYS_BOOT_GET_KBD
 
 config RISCV
-	bool "riscv architecture"
+	bool "RISC-V architecture"
 	select SUPPORT_OF_CONTROL
 
 config SANDBOX