fix "sparseirq: use kstat_irqs_cpu on non-x86 architectures too"

Repair 0b0f0b1c

arch/alpha/kernel/irq.c: In function 'show_interrupts':
arch/alpha/kernel/irq.c:93: error: 'i' undeclared (first use in this function)
arch/alpha/kernel/irq.c:93: error: (Each undeclared identifier is reported only once
arch/alpha/kernel/irq.c:93: error: for each function it appears in.)

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>