Input: sirfsoc-onkey - drop the IRQF_SHARED flag

Since the IRQ handler always returns IRQ_HANDLED it means this irq is not
a shared IRQ at all. Or at least, the SW is not self-consistent now.

Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>