usb: dwc3: qcom: fix peripheral and OTG suspend

A recent commit implementing wakeup support in host mode instead broke
suspend for peripheral and OTG mode.

The hack that was added in the suspend path to determine the speed of
any device connected to the USB2 bus not only accesses internal driver
data for a child device, but also dereferences a NULL pointer or
accesses freed data when the controller is not acting as host.

There's no quick fix to the layering violation, but since reverting
would leave us with broken suspend in host mode with wakeup triggering
immediately, let's keep the hack for now.

Fix the immediate issues by only checking the host bus speed and
enabling wakeup interrupts when acting as host.

Fixes: 6895ea55

 ("usb: dwc3: qcom: Configure wakeup interrupts during suspend")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20220804151001.23612-7-johan+linaro@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>