OvmfPkg: Reference new Tcg2PlatformDxe in the build system for compilation

OvmfPkg: Reference new Tcg2PlatformDxe in the build system for compilation

Compile the Tcg2PlatformDxe related code now.

Cc: Rebecca Cran <rebecca@bsdio.com>
Cc: Peter Grehan <grehan@freebsd.org>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Jiewen Yao <Jiewen.yao@intel.com>