Maintainers: add TPM2 reviewers for OvmfPkg

Maintainers: add TPM2 reviewers for OvmfPkg

OVMF can be built with a significant amount of TPM2 code now; add
Marc-André and Stefan as Reviewers for TPM2-related patches.

Keep the list of "R" entries alphabetically sorted.

Cc: Andrew Fish <afish@apple.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Stefan Berger <stefanb@linux.ibm.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
[lersek@redhat.com: resolve conflict with commit 98fc52c44eee]