Drivers: hv: util: move kvp/vss function declarations to hyperv_vmbus.h

These declarations are internal to hv_util module and hv_fcopy_* declarations
already reside there.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Tested-by: Alex Ng <alexng@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>