m68k: 68000: fix warnings in 68000 interrupt handling

When building with W=1:

      CC      arch/m68k/68000/ints.o
    arch/m68k/68000/ints.c:77:6: warning: no previous prototype for ‘process_int’ [-Wmissing-prototypes]
     void process_int(int vec, struct pt_regs *fp)
          ^~~~~~~~~~~
    arch/m68k/68000/ints.c:153:13: warning: no previous prototype for ‘trap_init’ [-Wmissing-prototypes]
     void __init trap_init(void)
                 ^~~~~~~~~

Include linux/cpu.h to get the prototype for taps_init().
Create a local ints.h for prototype of process_int(). Also mark
process_int() as asmlinkage, since it is called from the first level
interrupt assembly handler.

Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>

arch/m68k/68000/ints.c

@@ -14,6 +14,7 @@
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
+#include <linux/cpu.h>
 #include <asm/traps.h>
 #include <asm/io.h>
 #include <asm/machdep.h>
@@ -26,6 +27,8 @@
 #include <asm/MC68328.h>
 #endif
 
+#include "ints.h"
+
 /* assembler routines */
 asmlinkage void system_call(void);
 asmlinkage void buserr(void);
@@ -74,7 +77,7 @@ asmlinkage irqreturn_t inthandler7(void);
  * into one vector and look in the blasted mask register...
  * This code is designed to be fast, almost constant time, not clean!
  */
-void process_int(int vec, struct pt_regs *fp)
+asmlinkage void process_int(int vec, struct pt_regs *fp)
 {
 	int irq;
 	int mask;

arch/m68k/68000/ints.h

@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <linux/linkage.h>
+
+struct pt_regs;
+
+asmlinkage void process_int(int vec, struct pt_regs *fp);