m68k: mm: Add and use "fault.h"

When building with W=1:

    arch/m68k/mm/fault.c:22:5: warning: no previous prototype for ‘send_fault_sig’ [-Wmissing-prototypes]
       22 | int send_fault_sig(struct pt_regs *regs)
	  |     ^~~~~~~~~~~~~~
    arch/m68k/mm/fault.c:68:5: warning: no previous prototype for ‘do_page_fault’ [-Wmissing-prototypes]
       68 | int do_page_fault(struct pt_regs *regs, unsigned long address,
	  |     ^~~~~~~~~~~~~

Fix this by introducing a new header file "fault.h" for holding the
prototypes of functions implemented in arch/m68k/mm/fault.c.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/ef004b8cfe4aac892aa0fb7714c2ed81a02a9b89.1694613528.git.geert@linux-m68k.org

arch/m68k/kernel/sys_m68k.c

@@ -35,8 +35,7 @@
 
 #include <asm/tlb.h>
 
-asmlinkage int do_page_fault(struct pt_regs *regs, unsigned long address,
-			     unsigned long error_code);
+#include "../mm/fault.h"
 
 asmlinkage long sys_mmap2(unsigned long addr, unsigned long len,
 	unsigned long prot, unsigned long flags,

arch/m68k/kernel/traps.c

@@ -42,6 +42,7 @@
 #include <asm/tlbflush.h>
 
 #include "traps.h"
+#include "../mm/fault.h"
 
 static const char *vec_names[] = {
 	[VEC_RESETSP]	= "RESET SP",
@@ -126,10 +127,6 @@ static const char *space_names[] = {
 };
 
 void die_if_kernel(char *,struct pt_regs *,int);
-asmlinkage int do_page_fault(struct pt_regs *regs, unsigned long address,
-                             unsigned long error_code);
-int send_fault_sig(struct pt_regs *regs);
-
 asmlinkage void trap_c(struct frame *fp);
 
 #if defined (CONFIG_M68060)

arch/m68k/mm/fault.c

@@ -17,6 +17,8 @@
 #include <asm/setup.h>
 #include <asm/traps.h>
 
+#include "fault.h"
+
 extern void die_if_kernel(char *, struct pt_regs *, long);
 
 int send_fault_sig(struct pt_regs *regs)

arch/m68k/mm/fault.h

+/* SPDX-License-Identifier: GPL-2.0 */
+
+struct pt_regs;
+
+int do_page_fault(struct pt_regs *regs, unsigned long address,
+		  unsigned long error_code);
+int send_fault_sig(struct pt_regs *regs);