net: ipa: enable wakeup on IPA interrupt

Now that we handle wakeup interrupts properly, arrange for the IPA
interrupt to be treated as a wakeup interrupt.

Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>