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 commit 80006dbe ("kprobes/x86:
Remove jprobe implementation") has removed the caller in kprobes.
So this doesn't exist anymore.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.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);