xtensa: drop variant IRQ support

If an xtensa core provides an additional IRQ controller it should be
treated as a separate piece of hardware and be driven by an irqchip
driver.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/kernel/irq.c

@@ -158,7 +158,6 @@ void __init init_IRQ(void)
 #ifdef CONFIG_SMP
 	ipi_init();
 #endif
-	variant_init_irq();
 }
 
 #ifdef CONFIG_HOTPLUG_CPU