ArmVirtPkg: QemuFwCfgToPcdDxe: set SMBIOS entry point version dynamically

(This patch parallels OvmfPkg commit 37baf06b (SVN r17676).)

PcdSmbiosVersion controls the version number of the SMBIOS entry point
table (and other, related things) that the universal
"MdeModulePkg/Universal/SmbiosDxe" driver, providing EFI_SMBIOS_PROTOCOL,
installs.

The "virt" machine type of QEMU generates SMBIOS payload for the firmware
to install. The payload includes the entry point table ("anchor" table).
OvmfPkg/SmbiosPlatformDxe cannot install the anchor table (because that is
the jurisdiction of the generic "MdeModulePkg/Universal/SmbiosDxe"
driver); however, we can parse the entry point version from QEMU's anchor
table, and instruct "MdeModulePkg/Universal/SmbiosDxe" to adhere to that
version.

As default for PcdSmbiosVersion we should keep the current 0x0300 value
(ie. SMBIOS 3.0) from "MdeModulePkg/MdeModulePkg.dec"; that spec version
was specifically created for ARM / AARCH64 needs.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18043 6f19259b-4bc3-4df7-8a09-765794883524