There's been a reproducable USB OHCI/EHCI cpuidle related hang on omap4
for a while that happens after about 20 - 40 minutes on an idle system
with some data feeding device being connected, like a USB GPS device or
a cellular modem.

This issue happens in cpuidle states C2 and C3 and does not happen if
cpuidle is limited to C1 state only. The symptoms are that the whole
system hangs and never wakes up from idle, and if a watchdog is
configured the system reboots after a while.

Turns out that OHCI/EHCI devices on omap4 are trying to use the GIC
interrupt controller directly as a parent instead of the WUGEN. We
need to pass the interrupts through WUGEN to GIC to provide the wakeup
events for the processor.

Let's fix the issue by removing the gic interrupt-parent and use the
default interrupt-parent wakeupgen instead. Note that omap5.dtsi had
this already fixes earlier by commit 7136d457 ("ARM: omap: convert
wakeupgen to stacked domains") but we somehow missed omap4 at that
point.

Fixes: 7136d457 ("ARM: omap: convert wakeupgen to stacked domains")
Cc: Dave Gerlach <d-gerlach@ti.com>
Cc: Nishanth Menon <nm@ti.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Reviewed-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>