UefiCpuPkg/MpInitLib: Use AmdSvsmSnpVmsaRmpAdjust() to set/clear VMSA

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4654

The RMPADJUST instruction is used to change the VMSA attribute of a page,
but the VMSA attribute can only be changed when running at VMPL0. To
prepare for running at a less priviledged VMPL, use the AmdSvsmLib library
API to perform the RMPADJUST. The AmdSvsmLib library will perform the
proper operation on behalf of the caller.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Ray Ni <ray.ni@intel.com>

UefiCpuPkg/Library/MpInitLib/MpLib.h

@@ -883,20 +883,6 @@ FillExchangeInfoDataSevEs (
   IN volatile MP_CPU_EXCHANGE_INFO  *ExchangeInfo
   );
 
-/**
-  Issue RMPADJUST to adjust the VMSA attribute of an SEV-SNP page.
-
-  @param[in]  PageAddress
-  @param[in]  VmsaPage
-
-  @return  RMPADJUST return value
-**/
-UINT32
-SevSnpRmpAdjust (
-  IN  EFI_PHYSICAL_ADDRESS  PageAddress,
-  IN  BOOLEAN               VmsaPage
-  );
-
 /**
   Create an SEV-SNP AP save area (VMSA) for use in running the vCPU.