Staging: hv: Create a common header for all hyperv drivers to include

Staging: hv: Create a common header for all hyperv drivers to include

Create a common header for all hyperv drivers to include. When
we exit staging, this would land under include/linux.

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