hw/smbios: add stub for smbios_get_table_legacy()

hw/smbios: add stub for smbios_get_table_legacy()

QEMU build fails with

  hw/i386/fw_cfg.c:74: undefined reference to `smbios_get_table_legacy'

when it's built with only 'microvm' enabled i.e. with config patch

   +++ b/configs/devices/i386-softmmu/default.mak
   @@ -26,7 +26,7 @@

   # Boards:
   #
   -CONFIG_ISAPC=y
   -CONFIG_I440FX=y
   -CONFIG_Q35=y
   +CONFIG_ISAPC=n
   +CONFIG_I440FX=n
   +CONFIG_Q35=n

It happens because I've fogotten/lost smbios_get_table_legacy() stub.

Fix it by adding missing stub as Philippe suggested.

Fixes: b42b0e4daaa5 "smbios: build legacy mode code only for 'pc' machine"
Reported-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-ID: <20240326122630.85989-1-imammedo@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>