MIPS: OCTEON: fix unreachable code in octeon_irq_init_ciu

The type of 'r' in octeon_irq_init_ciu is 'unsigned int', so 'r < 0'
can't be true.

Fix this by change the type of 'r' and 'i' from 'unsigned int'
to 'int'. As 'i' won't be negative, this change works.

Fixes: 99fbc70 ("MIPS: Octeon: irq: Alloc desc before configuring IRQ")
Signed-off-by: Menglong Dong <dong.menglong@zte.com.cn>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Author: Menglong Dong

arch/mips/cavium-octeon/octeon-irq.c

@@ -1444,7 +1444,7 @@ static void octeon_irq_setup_secondary_ciu2(void)
 static int __init octeon_irq_init_ciu(
 	struct device_node *ciu_node, struct device_node *parent)
 {
-	unsigned int i, r;
+	int i, r;
 	struct irq_chip *chip;
 	struct irq_chip *chip_edge;
 	struct irq_chip *chip_mbox;