[MIPS] do_IRQ cleanup

Now we have both function and macro version of do_IRQ() and the former
is used only by DEC and non-preemptive kernel.  This patch makes
everyone use the macro version and removes the function version.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/dec/setup.c

@@ -761,3 +761,9 @@ void __init arch_init_irq(void)
 	if (dec_interrupt[DEC_IRQ_HALT] >= 0)
 		setup_irq(dec_interrupt[DEC_IRQ_HALT], &haltirq);
 }
+
+asmlinkage unsigned int dec_irq_dispatch(unsigned int irq)
+{
+	do_IRQ(irq);
+	return 0;
+}