Drivers: hv: vmbus: Removed an unnecessary cast from void *

In C, we don't need such a cast.

Fixes: ae20b254 ("Drivers: hv: vmbus: enable VMBus protocol version 5.0")
Reported-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>