sh: intc: Fix sense regs oops for IRL IRQs.

IRL doesn't always define sense registers, so don't bother trying to
iterate through the table. This ended up causing an oops on SH-X3
when using IRL mode.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/kernel/cpu/irq/intc.c

@@ -218,7 +218,7 @@ static int intc_set_sense(unsigned int irq, unsigned int type)
 		break;
 	}
 
-	if (!enum_id || !value)
+	if (!enum_id || !value || !desc->sense_regs)
 		return -EINVAL;
 
 	value ^= VALID(0);