[MIPS] Fix compiler warnings in arch/mips/sibyte/bcm1480/irq.c

Fix the following compiler warnings:

  CC      arch/mips/sibyte/bcm1480/irq.o
arch/mips/sibyte/bcm1480/irq.c: In function ‘bcm1480_set_affinity’:
arch/mips/sibyte/bcm1480/irq.c:168: warning: ISO C90 forbids mixed declarations and code
arch/mips/sibyte/bcm1480/irq.c: In function ‘ack_bcm1480_irq’:
arch/mips/sibyte/bcm1480/irq.c:230: warning: ISO C90 forbids mixed declarations and code

Signed-off-by: Martin Michlmayr <tbm@cyrius.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>