[MIPS] IP27: Don't destroy interrupt routing information on shutdown irq.

This fixes the "not syncing: Could not identify cpu/level ..." panic
when a PCI irq is requested the second time.
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/sgi-ip27/ip27-irq.c

@@ -296,7 +296,6 @@ static void shutdown_bridge_irq(unsigned int irq)
 	struct bridge_controller *bc = IRQ_TO_BRIDGE(irq);
 	struct hub_data *hub = hub_data(cpu_to_node(bc->irq_cpu));
 	bridge_t *bridge = bc->base;
-	struct slice_data *si = cpu_data[bc->irq_cpu].data;
 	int pin, swlevel;
 	cpuid_t cpu;
 
@@ -311,7 +310,6 @@ static void shutdown_bridge_irq(unsigned int irq)
 	intr_disconnect_level(cpu, swlevel);
 
 	__clear_bit(swlevel, hub->irq_alloc_mask);
-	si->level_to_irq[swlevel] = -1;
 
 	bridge->b_int_enable &= ~(1 << pin);
 	bridge->b_wid_tflush;