USB: EHCI: msm: Add support for power management

Enable runtime PM and mark no_callbacks flag.  OTG device, parent of
HCD takes care of putting hardware into low power mode.  Adjust port
power wakeup flags during system suspend and resume.

Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>