When compiling with W=1 enabling -Wmissing-prototypes the compiler
warns:

  arch/openrisc/kernel/traps.c:67:6: error: no previous prototype for 'show_registers' [-Werror=missing-prototypes]

Fix by adding the prototype to the appropriate header file and including
the header file in the appropriate C files.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Closes: https://lore.kernel.org/linux-kernel/20230810141947.1236730-17-arnd@kernel.org/
Signed-off-by: Stafford Horne <shorne@gmail.com>
---
 arch/openrisc/include/asm/processor.h | 1 +
 arch/openrisc/kernel/process.c        | 2 --
 arch/openrisc/kernel/traps.c          | 1 +
 3 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/openrisc/include/asm/processor.h b/arch/openrisc/include/asm/processor.h
index ed9efb430afa..3b736e74e6ed 100644
--- a/arch/openrisc/include/asm/processor.h
+++ b/arch/openrisc/include/asm/processor.h
@@ -73,6 +73,7 @@ struct thread_struct {
 
 void start_thread(struct pt_regs *regs, unsigned long nip, unsigned long sp);
 unsigned long __get_wchan(struct task_struct *p);
+void show_registers(struct pt_regs *regs);
 
 #define cpu_relax()     barrier()
 
diff --git a/arch/openrisc/kernel/process.c b/arch/openrisc/kernel/process.c
index dfa558f98ed8..a07512de0169 100644
--- a/arch/openrisc/kernel/process.c
+++ b/arch/openrisc/kernel/process.c
@@ -119,8 +119,6 @@ void flush_thread(void)
 
 void show_regs(struct pt_regs *regs)
 {
-	extern void show_registers(struct pt_regs *regs);
-
 	show_regs_print_info(KERN_DEFAULT);
 	/* __PHX__ cleanup this mess */
 	show_registers(regs);
diff --git a/arch/openrisc/kernel/traps.c b/arch/openrisc/kernel/traps.c
index afa47501118f..f221e4b4298f 100644
--- a/arch/openrisc/kernel/traps.c
+++ b/arch/openrisc/kernel/traps.c
@@ -31,6 +31,7 @@
 #include <linux/uaccess.h>
 
 #include <asm/io.h>
+#include <asm/processor.h>
 #include <asm/unwinder.h>
 #include <asm/sections.h>
 
-- 
2.39.1