USB: Add call to notify xHC of a device reset.

Add a new host controller driver method, reset_device(), that the USB core
will use to notify the host of a successful device reset.  The call may
fail due to out-of-memory errors; attempt the port reset sequence again if
that happens.  Update hub_port_init() to allow resetting a configured
device.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>