xhci-plat: Mark usb1 and usb2 devices as wakeup source

Currently usb1 and usb2 root devices are marked as wakeup capable
i.e. dev->power.can_wakeup but not set as wakeup source i.e.
dev->power.wakeup is NULL. When system suspend is being invoked,
usb_suspend() is called from PM core context which tries to match
wakeup capability with remote wakeup functionality. choose_wakeup()
API gets wakeup capability using device_may_wakeup() API which return
false (due to dev->power.wakeup is NULL). USB core sees this as
mismatch between wakeup capability and remote wakeup functionality
and resume usb1/usb2 which results into resuming USB controller
(parent of those devices). Fix this issue by marking usb1 and usb2
devices as wakeup source using device_wakeup_enable() API.

Change-Id: Ia858795c80f8852d696fd3c19ed442de1b3f1ac3
Signed-off-by: Mayank Rana <mrana@codeaurora.org>