mb/google/volteer/var/terrador: Enable audio SMBIOS OEM string

mb/google/volteer/var/terrador: Enable audio SMBIOS OEM string

It needs to use probe statement in overridetree.cb to enable the cache
of fw_config field implemented by cb:44782 and cb:44783.

BUG=b:161963281
TEST= dmidecode -t 11 shows correct audio fw_config.
Handle 0x0009, DMI type 11, 5 bytes
OEM Strings
	String 1: DB_USB-USB4_GEN2
	String 2: AUDIO-MAX98373_ALC5682I_I2S_UP4

Signed-off-by: Kevin Cheng <kevin.cheng@intel.com>
Change-Id: I68c19b67d945aaca3e9ebec87eb27a4b07e1a49e
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45673
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Sathyanarayana Nujella <sathyanarayana.nujella@intel.com>
Reviewed-by: David Wu <david_wu@quanta.corp-partner.google.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>