usb: Initialize hcd->state roothubs.

We would like to allow host controller drivers to stop using hcd->state.
Unfortunately, some host controller drivers use hcd->state as an
implicit way of telling the core that a controller has died.  The
roothub registration functions must assume the host died if hcd->state
equals HC_STATE_HALT.

To facilitate drivers that don't want to set hcd->state to
HC_STATE_RUNNING in their initialization routines, we set the state to
running before calling the host controller's start function.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>