Staging: hv: util: Make hv_utils a vmbus device driver

In preperation for supporting auto-loading the util driver, make
the util driver a vmbus 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>