kprobes: Remove show_registers() function prototype

Remove show_registers() function prototype because this function
has been renamed by commit:

  57da8b96 ("x86: Avoid double stack traces with show_regs()")

and this commit has removed the caller in kprobes altogether:

  80006dbe ("kprobes/x86: Remove jprobe implementation")

So this doesn't exist anymore - remove the orphan prototype.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/kprobes.h

@@ -227,7 +227,6 @@ extern int arch_prepare_kprobe(struct kprobe *p);
 extern void arch_arm_kprobe(struct kprobe *p);
 extern void arch_disarm_kprobe(struct kprobe *p);
 extern int arch_init_kprobes(void);
-extern void show_registers(struct pt_regs *regs);
 extern void kprobes_inc_nmissed_count(struct kprobe *p);
 extern bool arch_within_kprobe_blacklist(unsigned long addr);
 extern int arch_populate_kprobe_blacklist(void);