Drivers: hv: Add new message types to enhance KVP

Add additional KVP (Key Value Pair) protocol  messages to
enhance KVP functionality for Linux guests on Hyper-V. As part of this,
patch define an explicit version negoitiation message.

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