greybus: hd: fix host-device life time issues

Fix host-device life time issues by separating host-device allocation
from registration.

This is needed both to make sure that all host-device resources are
available before registering the device and to prevent such resources
from being deallocated while the device is still in use during device
removal.

This specifically fixes the following warnings during es1 and es2
disconnect:

usb 1-1.1: No free CPort OUT urbs, having to dynamically allocate one!

Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>