add NIOS2 to newlib supported architectures

target/config/Config.in.libc

@@ -65,6 +65,7 @@ config ADK_TARGET_LIB_NEWLIB
 		ADK_TARGET_ARCH_LM32 || \
 		ADK_TARGET_ARCH_MICROBLAZE || \
 		ADK_TARGET_ARCH_MIPS || \
+		ADK_TARGET_ARCH_NIOS2 || \
 		ADK_TARGET_ARCH_MOXIE || \
 		ADK_TARGET_ARCH_NDS32 || \
 		ADK_TARGET_ARCH_OR1K || \