bcm63xx: ext_intc: fix warning

In file included from ./arch/mips/include/asm/io.h:34,
                 from ./arch/mips/include/asm/mmiowb.h:5,
                 from ./include/linux/spinlock.h:60,
                 from ./include/linux/irq.h:14,
                 from drivers/irqchip/irq-bcm6345-ext.c:10:
drivers/irqchip/irq-bcm6345-ext.c: In function 'bcm6345_ext_intc_of_init':
./arch/mips/include/asm/mach-bcm63xx/ioremap.h:48:9: warning: 'base' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return is_bcm63xx_internal_registers((unsigned long)addr);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/irqchip/irq-bcm6345-ext.c:255:16: note: 'base' was declared here
  void __iomem *base;
                ^~~~

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
(cherry picked from commit 29c3bb5f41)

target/linux/brcm63xx/patches-4.14/325-irqchip-bcm6345-external-fix-base-uninitialized.patch

@@ -0,0 +1,28 @@
+--- a/drivers/irqchip/irq-bcm6345-ext.c
++++ b/drivers/irqchip/irq-bcm6345-ext.c
+@@ -271,21 +271,19 @@ static int __init bcm6345_ext_intc_of_in
+ 
+ 	for (i = 0; i < num_irqs; i++) {
+ 		irqs[i] = irq_of_parse_and_map(node, i);
+-		if (!irqs[i]) {
+-			ret = -ENOMEM;
+-			goto out_unmap;
+-		}
++		if (!irqs[i])
++			return -ENOMEM;
+ 	}
+ 
+ 	base = of_iomap(node, 0);
+ 	if (!base)
+-		goto out_unmap;
++		return -ENXIO;
+ 
+ 	ret = __bcm6345_ext_intc_init(node, num_irqs, irqs, base, shift,
+ 				      toggle_clear_on_ack);
+ 	if (!ret)
+ 		return 0;
+-out_unmap:
++
+ 	iounmap(base);
+ 
+ 	for (i = 0; i < num_irqs; i++)