armv7 ampintc uses ampintc_intr_string(), unused on arm64

diff --git sys/arch/arm64/dev/ampintc.c sys/arch/arm64/dev/ampintc.c
index 3c0ccb8ed47..ec8c9f3afa9 100644
--- sys/arch/arm64/dev/ampintc.c
+++ sys/arch/arm64/dev/ampintc.c
@@ -185,7 +185,6 @@ void		*ampintc_intr_establish_fdt(void *, int *, int,
 		    struct cpu_info *, int (*)(void *), void *, char *);
 void		 ampintc_intr_disestablish(void *);
 void		 ampintc_irq_handler(void *);
-const char	*ampintc_intr_string(void *);
 uint32_t	 ampintc_iack(void);
 void		 ampintc_eoi(uint32_t);
 void		 ampintc_set_priority(int, int);
@@ -897,16 +896,6 @@ ampintc_intr_disestablish(void *cookie)
 	free(ih, M_DEVBUF, sizeof(*ih));
 }
 
-const char *
-ampintc_intr_string(void *cookie)
-{
-	struct intrhand *ih = (struct intrhand *)cookie;
-	static char irqstr[1 + sizeof("ampintc irq ") + 4];
-
-	snprintf(irqstr, sizeof irqstr, "ampintc irq %d", ih->ih_irq);
-	return irqstr;
-}
-
 /*
  * GICv2m frame controller for MSI interrupts.
  */