usb: dwc3-msm: Add support for snps SSPHY suspend in system suspend

Currently the platforms using SNPS SSPHY do not suspend it so as
to receive SS wakeup events via pwr_event_irq. But certain
telematics platforms do not need SS wakeup in system suspend
scenario. Add devicetree flag 'qcom,no-wakeup-from-pm-suspend'
support and based on this flag, allow SSPHY suspend to happen as
a part of system suspend, even if SS/no device is connected.

Change-Id: I691585e15539490e63a345fe2b3aacf182352399
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>