Staging: hv: add the Hyper-V api header files

These are the header files for the API to talk to the Hyper-V
core.

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