riscv: remove cpu_stop()

Except arch_cpu_idle_dead(), no users of this function. So remove
cpu_stop() and fold its code into arch_cpu_idle_dead().
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/include/asm/smp.h

@@ -63,8 +63,6 @@ asmlinkage void smp_callin(void);
 #if defined CONFIG_HOTPLUG_CPU
 int __cpu_disable(void);
 void __cpu_die(unsigned int cpu);
-void cpu_stop(void);
-#else
 #endif /* CONFIG_HOTPLUG_CPU */
 
 #else

arch/riscv/kernel/cpu-hotplug.c

@@ -14,12 +14,6 @@
 #include <asm/cpu_ops.h>
 #include <asm/sbi.h>
 
-void cpu_stop(void);
-void arch_cpu_idle_dead(void)
-{
-	cpu_stop();
-}
-
 bool cpu_has_hotplug(unsigned int cpu)
 {
 	if (cpu_ops[cpu]->cpu_stop)
@@ -75,7 +69,7 @@ void __cpu_die(unsigned int cpu)
 /*
  * Called from the idle thread for the CPU which has been shutdown.
  */
-void cpu_stop(void)
+void arch_cpu_idle_dead(void)
 {
 	idle_task_exit();