Staging: hv: hv_mouse: clean up version structure usage

Turns out no one uses the major or minor fields, but hey, we'll keep
them around just to make people feel happy...

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