greybus: es1.c: wait until the last possible minute to start the svc messages

When initializing the USB device, we were starting up the svc message
queue before the cport urbs were allocated.  This might not be an issue
for "slower" machines, but not having any allocated urbs for a cport
might be an issue if we were to handle svc messages.

So wait until everything is properly initialized and allocated before
starting the svc urb.

Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>