ath10k: don't consume other's shared interrupts

ath10k assumed all interrupts were directed to it.
This isn't the case for legacy shared interrupts.
ath10k consumed interrupts for other devices.

Check device irq status and return IRQ_NONE when
appropriate.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>