Staging: hv: Implement key/value pair (KVP)

This is an implementation of the key value/pair (KVP) functionality
for Linux guests hosted on HyperV. This component communicates
with the host to support the KVP functionality.

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