platform: Drop irqchip warm init and exit hooks

Now that driver lifecycle is managed from within the SBI irqchip core,
platforms need only to initialize the driver once during cold init.
Remove the remaining platform hooks that are no longer used.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

platform/template/platform.c

@@ -87,20 +87,12 @@ static int platform_final_init(bool cold_boot)
 }
 
 /*
- * Initialize the platform interrupt controller for current HART.
+ * Initialize the platform interrupt controller during cold boot.
  */
-static int platform_irqchip_init(bool cold_boot)
+static int platform_irqchip_init(void)
 {
-	int ret;
-
 	/* Example if the generic PLIC driver is used */
-	if (cold_boot) {
-		ret = plic_cold_irqchip_init(&plic);
-		if (ret)
-			return ret;
-	}
-
-	return 0;
+	return plic_cold_irqchip_init(&plic);
 }
 
 /*