irq: error missed ifndef CONFIG_HAVE_SPARSE_IRQ

An error return from create_irq_nr() is 0, but an error return from
create_irq() is -1.

Signed-off-by: Dean Nelson <dcn@sgi.com>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>