m68k: Add common forward declaration for show_registers()

There are several forward declarations for show_registers() in C source
files.  Replace these by a single common forward declaration in
<asm/processor.h>, and include <asm/processor.h> where needed.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Link: https://lore.kernel.org/r/d5b6a7f9af3e82f0ccb67edac09d9ee45d457932.1657114791.git.geert@linux-m68k.org

arch/m68k/include/asm/processor.h

@@ -151,6 +151,7 @@ static inline void release_thread(struct task_struct *dead_task)
 }
 
 unsigned long __get_wchan(struct task_struct *p);
+void show_registers(struct pt_regs *regs);
 
 #define	KSTK_EIP(tsk)	\
     ({			\

arch/m68k/kernel/traps.c

@@ -36,6 +36,7 @@
 #include <linux/uaccess.h>
 #include <asm/traps.h>
 #include <asm/machdep.h>
+#include <asm/processor.h>
 #include <asm/siginfo.h>
 #include <asm/tlbflush.h>
 

arch/m68k/mac/macints.c

@@ -126,8 +126,7 @@
 #include <asm/mac_baboon.h>
 #include <asm/hwtest.h>
 #include <asm/irq_regs.h>
-
-extern void show_registers(struct pt_regs *);
+#include <asm/processor.h>
 
 static unsigned int mac_irq_startup(struct irq_data *);
 static void mac_irq_shutdown(struct irq_data *);

arch/m68k/virt/ints.c

@@ -12,6 +12,7 @@
 #include <asm/hwtest.h>
 #include <asm/irq.h>
 #include <asm/irq_regs.h>
+#include <asm/processor.h>
 #include <asm/virt.h>
 
 #define GFPIC_REG_IRQ_PENDING           0x04
@@ -19,8 +20,6 @@
 #define GFPIC_REG_IRQ_DISABLE           0x0c
 #define GFPIC_REG_IRQ_ENABLE            0x10
 
-extern void show_registers(struct pt_regs *regs);
-
 static struct resource picres[6];
 static const char *picname[6] = {
 	"goldfish_pic.0",