Staging: hv: vmbus: Introduce vmbus ID space in struct hv_driver

In preparation for supporting auto-loading Hyper-V drivers
using vmbus specific aliases, introduce vmbus ID space in struct hv_driver.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>