genirq: Fix unnecessary automatic type conversion

kstat_irqs is unsigned int and the return type of kstat_irqs() is also
unsigned int so sum should be unsigned int as well even if the result
is correct due to automatic type conversion.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Link: http://lkml.kernel.org/r/1430642930-23929-1-git-send-email-hofrat@osadl.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/irq/irqdesc.c

@@ -619,7 +619,7 @@ unsigned int kstat_irqs(unsigned int irq)
 {
 	struct irq_desc *desc = irq_to_desc(irq);
 	int cpu;
-	int sum = 0;
+	unsigned int sum = 0;
 
 	if (!desc || !desc->kstat_irqs)
 		return 0;