OvmfPkg: implement EFI_SMM_CONTROL2_PROTOCOL with a DXE_RUNTIME_DRIVER

OvmfPkg: implement EFI_SMM_CONTROL2_PROTOCOL with a DXE_RUNTIME_DRIVER

The EFI_SMM_COMMUNICATION_PROTOCOL implementation that is provided by the
SMM core depends on EFI_SMM_CONTROL2_PROTOCOL; see the
mSmmControl2->Trigger() call in the SmmCommunicationCommunicate() function
[MdeModulePkg/Core/PiSmmCore/PiSmmIpl.c].

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Michael Kinney <michael.d.kinney@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19042 6f19259b-4bc3-4df7-8a09-765794883524