riscv: ax25: bypass malloc when spl fit boots from ram

When fit image boots from ram, the payload will
be prepared in the address of SPL_LOAD_FIT_ADDRESS.
In spl fit generic flow, it will malloc another
memory address and copy whole fit image to this
malloc address.  But it is un-necessary for booting
from RAM.

This patch improves this flow by declare the
board_spl_fit_buffer_addr() to replace the original one.
The larger image size (eq: Kernel Image 10~20MB), it
can save more booting time.

Signed-off-by: Rick Chen <rick@andestech.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

arch/riscv/cpu/ax25/Makefile

@@ -5,3 +5,4 @@
 
 obj-y	:= cpu.o
 obj-y	+= cache.o
+obj-y	+= spl.o

arch/riscv/cpu/ax25/spl.c

@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2023 Andes Technology Corporation
+ * Rick Chen, Andes Technology Corporation <rick@andestech.com>
+ */
+#include <common.h>
+#include <cpu_func.h>
+#include <hang.h>
+#include <init.h>
+#include <log.h>
+#include <spl.h>
+#include <asm/global_data.h>
+#include <asm/system.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+#if CONFIG_IS_ENABLED(RAM_SUPPORT)
+struct legacy_img_hdr *spl_get_load_buffer(ssize_t offset, size_t size)
+{
+	return (void *)(CONFIG_SPL_LOAD_FIT_ADDRESS + offset);
+}
+
+void *board_spl_fit_buffer_addr(ulong fit_size, int sectors, int bl_len)
+{
+	return spl_get_load_buffer(0, sectors * bl_len);
+}
+#endif