If we don't have an out-of-band wakeup IRQ configured through DT (as
most platforms don't), then we fall out of this function with
'irq_wakeup == 0'. Other code (e.g., mwifiex_disable_wake() and
mwifiex_enable_wake()) treats 'irq_wakeup >= 0' as a valid IRQ, and so
we end up calling {enable,disable}_irq() on IRQ 0.

That seems bad, so let's not do that.

Same problem as fixed in this patch:

https://patchwork.kernel.org/patch/9531693/
[PATCH v2 2/3] btmrvl: set irq_bt to -1 when failed to parse it

with the difference that:
(a) this one is actually a regression and
(b) this affects both device tree and non-device-tree systems

While fixing the regression, also drop the verbosity on the parse
failure, so we don't see this when a DT node is present but doesn't have
an interrupt property (this is perfectly legal):

[   21.999000] mwifiex_pcie 0000:01:00.0: fail to parse irq_wakeup from device tree

Fixes: 853402a0 ("mwifiex: Enable WoWLAN for both sdio and pcie")
Signed-off-by: Brian Norris <briannorris@chromium.org>
Acked-by: Rajat Jain <rajatja@google.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>