riscv: add prototypes for assembly language functions from head.S

Add prototypes for assembly language functions defined in head.S,
and include these prototypes into C source files that call those
functions.

This patch resolves the following warnings from sparse:

arch/riscv/kernel/setup.c:39:10: warning: symbol 'hart_lottery' was not declared. Should it be static?
arch/riscv/kernel/setup.c:42:13: warning: symbol 'parse_dtb' was not declared. Should it be static?
arch/riscv/kernel/smpboot.c:33:6: warning: symbol '__cpu_up_stack_pointer' was not declared. Should it be static?
arch/riscv/kernel/smpboot.c:34:6: warning: symbol '__cpu_up_task_pointer' was not declared. Should it be static?
arch/riscv/mm/fault.c:25:17: warning: symbol 'do_page_fault' was not declared. Should it be static?

This change should have no functional impact.

Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>

arch/riscv/kernel/head.h

@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2019 SiFive, Inc.
+ */
+#ifndef __ASM_HEAD_H
+#define __ASM_HEAD_H
+
+#include <linux/linkage.h>
+#include <linux/init.h>
+
+extern atomic_t hart_lottery;
+
+asmlinkage void do_page_fault(struct pt_regs *regs);
+asmlinkage void __init setup_vm(uintptr_t dtb_pa);
+
+extern void *__cpu_up_stack_pointer[];
+extern void *__cpu_up_task_pointer[];
+
+void __init parse_dtb(void);
+
+#endif /* __ASM_HEAD_H */

arch/riscv/kernel/setup.c

@@ -24,6 +24,8 @@
 #include <asm/tlbflush.h>
 #include <asm/thread_info.h>
 
+#include "head.h"
+
 #ifdef CONFIG_DUMMY_CONSOLE
 struct screen_info screen_info = {
 	.orig_video_lines	= 30,

arch/riscv/kernel/smpboot.c

@@ -30,6 +30,8 @@
 #include <asm/sections.h>
 #include <asm/sbi.h>
 
+#include "head.h"
+
 void *__cpu_up_stack_pointer[NR_CPUS];
 void *__cpu_up_task_pointer[NR_CPUS];
 static DECLARE_COMPLETION(cpu_running);

arch/riscv/mm/fault.c

@@ -18,6 +18,8 @@
 #include <asm/ptrace.h>
 #include <asm/tlbflush.h>
 
+#include "../kernel/head.h"
+
 /*
  * This routine handles page faults.  It determines the address and the
  * problem, and then passes it off to one of the appropriate routines.

arch/riscv/mm/init.c

@@ -19,6 +19,8 @@
 #include <asm/pgtable.h>
 #include <asm/io.h>
 
+#include "../kernel/head.h"
+
 unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
 							__page_aligned_bss;
 EXPORT_SYMBOL(empty_zero_page);