StandaloneMmPkg/Core: Switch to MM HobList after MM HostList is ready

Switch to MM HobList as soon as MM HostList is initialized to avoid
StandaloneMmCore still using the HobList which is outside of MMRAM.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Signed-off-by: Wei6 Xu <wei6.xu@intel.com>

StandaloneMmPkg/Core/StandaloneMmCore.c

@@ -703,6 +703,7 @@ StandaloneMmMain (
   CopyMem (MmHobStart, HobStart, HobSize);
   Status = MmInstallConfigurationTable (&gMmCoreMmst, &gEfiHobListGuid, MmHobStart, HobSize);
   ASSERT_EFI_ERROR (Status);
+  gHobList = MmHobStart;
 
   //
   // Register notification for EFI_MM_CONFIGURATION_PROTOCOL registration and