OvmfPkg/PlatformPei: factor out Q35BoardVerification()

OvmfPkg/PlatformPei: factor out Q35BoardVerification()

Before adding another SMM-related, and therefore Q35-only, dynamically
detectable feature, extract the current board type check from
Q35TsegMbytesInitialization() to a standalone function.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1512
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Message-Id: <20200129214412.2361-5-lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>