usb: xhci-plat: Enable wakeup for the root hubs

During system suspend, usb_suspend() will get called for
both root hub instances and in the choose_wakeup() routine
it will find that device_may_wakeup() returns false. If
the busses were previously runtime suspended then
udev->do_remote_wakeup would be set, but since it conflicts
with the wakeup setting being false, the routine has to
first runtime resume the devices in order to change the
remote wakeup setting. This causes unnecessary delay
as it interrupts the system suspend sequence.

Since the host already does support remote wakeup, enable the
per-device wakeup settings for both the hcd root hub instances
in order to avoid the mismatch during choose_wakeup() which
will allow usb_suspend() to proceed without any unnecessary
resume.

Change-Id: I619272c5d0439427061541f5658cfd305a4ebd46
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Signed-off-by: Mayank Rana <mrana@codeaurora.org>