usb: dwc3: Add support for PM suspend and hibernation in host mode

DWC3 driver uses wakeup_source and allows pm_suspend only after
entering low power mode as part of runtime suspend. This prevents
PM suspend in host mode if connected device's driver doesn't
support runtime or selective suspend.
For platforms such as automotive, add support in driver where
user can specify using dtsi attribute to not use wakeup source in
host mode. It will allow system to enter deep sleep or pm_suspend
irrespective of runtime PM state of XHCI. The connected devices
are also reset-resumed on PM resume.
On high level below are the changes in default behavior:
 -Do not use wakeup_source for DWC3 when operating in host mode.
 -For host mode, devices will suspend upon PM suspend and
  reset-resumed on PM resume.

Change-Id: I8a3d744a1d9d714f17a0cfe4ff5b69b04d9f763f
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>