riscv: cpu: generic: fallback to generic cleanup_before_linux()

The current implementation is equivalent to the fallback one, so
this shouldn't change any behaviour but cleans the code up only.

Signed-off-by: Yao Zi <ziyao@disroot.org>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

arch/riscv/cpu/generic/Makefile

@@ -3,4 +3,3 @@
 # Copyright (C) 2018, Bin Meng <bmeng.cn@gmail.com>
 
 obj-y += dram.o
-obj-y += cpu.o

arch/riscv/cpu/generic/cpu.c

@@ -1,22 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0+
-/*
- * Copyright (C) 2018, Bin Meng <bmeng.cn@gmail.com>
- */
-
-#include <irq_func.h>
-#include <asm/cache.h>
-
-/*
- * cleanup_before_linux() is called just before we call linux
- * it prepares the processor for linux
- *
- * we disable interrupt and caches.
- */
-int cleanup_before_linux(void)
-{
-	disable_interrupts();
-
-	cache_flush();
-
-	return 0;
-}