qtnfmac: fix INTx interrupt handling

In the current implementation INTx interrupt is deasserted after the
control path processing. However this may lead to missed interrupts
from the wireless card. For instance, this may happen as a result
of control path activity, when another interrupt arrives before
INTx is deasserted.

Signed-off-by: Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>