USB: EHCI: Fix unclocked access by rhub_poll in bus_suspend

HCD core may try to get HUB's status even in bus suspend as
part of root hub polling. This can cause unclocked access.
Fix this by bailing out if RHUB state is not RUNNING.

Change-Id: I1b890b21e421770c09a74903ae5b19f1f1cc9616
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>