Add definitions for GetVpRegister and SetVpRegister hypercalls, which
are implemented for both x86 and ARM64.
Signed-off-by: NMichael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20200422195737.10223-5-mikelley@microsoft.comSigned-off-by: NWei Liu <wei.liu@kernel.org>