For SEV-ES, the GHCB page address is stored in the GHCB MSR register
(0xc0010130). Define the register and the format used for register
during GHCB protocol negotiation.
Cc: Michael D Kinney <michael.d.kinney@intel.com> Cc: Liming Gao <liming.gao@intel.com> Reviewed-by: Liming Gao <liming.gao@intel.com> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> Regression-tested-by: Laszlo Ersek <lersek@redhat.com>