usb: xhci-msm:hsic: Do not poll root hub after bus suspend

Root hub polling timer is not stopped after bus is
suspended. If timer expires after controller suspend this
causes un-clocked access to portsc register. Hence stop
root hub polling after bus suspend and start polling after
controller resume.

CRs-Fixed: 589141
Change-Id: Ic6006679cf90f92220339a9338cc5cf58ebc8f72
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>