usb: dwc3-msm: Allow Super speed phy suspend in P3 link state

In Super speed mode DWC3_GUSB3PIPECTL_SUSPHY bit is not set.
This does not allow super speed phy to enter suspend upon
usb bus suspend when link enters in P3 state. As a result no
IN_P3 power event irq is generated and controller suspend is
aborted. Hence set this bit for SS phy to enter suspend when
link goes to P3 state.

CRs-Fixed: 783610
Change-Id: I818c0740482e53d2b9b4724b46a4bc4677f7296c
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>