riscv: disable linux optimize for size option, does not link

target/linux/config/Config.in.kernel

@@ -248,7 +248,7 @@ config ADK_LINUX_KERNEL_HIGHMEM
 config ADK_LINUX_KERNEL_CC_OPTIMIZE_FOR_SIZE
 	bool "Optimize for size"
 	# does not boot in qemu-microblaze
-	depends on !ADK_TARGET_ARCH_MICROBLAZE
+	depends on !ADK_TARGET_ARCH_MICROBLAZE && !ADK_TARGET_ARCH_RISC64
 	default y