mb/google/volteer: Enable CnviBtAudioOffload

This change enables CnviBtAudioOffload. FSP is invoked to configure
BT over USB and BT I2S pins for cAVS connection.

BUG=b:169045123
TEST=Verifed CnviBtCore and CnviBtAudioOffload settings and FSP
configuration. Booted up to kernel on Volteer.

Signed-off-by: John Zhao <john.zhao@intel.com>
Change-Id: I1780da0824d145a79743d5cffdea4821236d4f74
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45586
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Naveen M <naveen.m@intel.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
diff --git a/src/mainboard/google/volteer/variants/baseboard/devicetree.cb b/src/mainboard/google/volteer/variants/baseboard/devicetree.cb
index 11542f8..43ba255 100644
--- a/src/mainboard/google/volteer/variants/baseboard/devicetree.cb
+++ b/src/mainboard/google/volteer/variants/baseboard/devicetree.cb
@@ -230,6 +230,8 @@
 
 	register "tcc_offset" = "10"     # TCC of 90
 
+	register "CnviBtAudioOffload" = "FORCE_ENABLE"
+
 	# Intel Common SoC Config
 	#+-------------------+---------------------------+
 	#| Field             |  Value                    |