[SPARC64]: Let irq_install_pre_handler() get called multiple times.

Signed-off-by: David S. Miller <[e-mail]>

arch/sparc64/kernel/irq.c

···
 	data->pre_handler_arg1 = arg1;
 	data->pre_handler_arg2 = arg2;
 
+	if (desc->chip == &sun4u_irq_ack ||
+	    desc->chip == &sun4v_irq_ack)
+		return;
+
 	desc->chip = (desc->chip == &sun4u_irq ?
 		      &sun4u_irq_ack : &sun4v_irq_ack);
 }