mb/intel/shadowmountain: Update HDMI audio mode to 8T

This patch sets the HDMI audio mode to 8T as required by the latest FSP
version v2081_02

TEST: HDMI audio codecs detection is failing without this change.

Change-Id: Ie5a825da7d199c9ee61e64d8f4ee7dec28fdaacd
Signed-off-by: Sugnan Prabhu S <sugnan.prabhu.s@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51273
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aamir Bohra <aamir.bohra@intel.com>
Reviewed-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-by: Rizwan Qureshi <rizwan.qureshi@intel.com>
diff --git a/src/mainboard/intel/shadowmountain/variants/baseboard/devicetree.cb b/src/mainboard/intel/shadowmountain/variants/baseboard/devicetree.cb
index e9284f4..4df8017 100644
--- a/src/mainboard/intel/shadowmountain/variants/baseboard/devicetree.cb
+++ b/src/mainboard/intel/shadowmountain/variants/baseboard/devicetree.cb
@@ -118,7 +118,7 @@
 	register "PchHdaAudioLinkSndwEnable[0]" = "0"
 	register "PchHdaAudioLinkSndwEnable[1]" = "0"
 	# iDisp-Link T-Mode 0: 2T, 2: 4T, 3: 8T, 4: 16T
-	register "PchHdaIDispLinkTmode" = "2"
+	register "PchHdaIDispLinkTmode" = "3"
 	# iDisp-Link Freq 4: 96MHz, 3: 48MHz.
 	register "PchHdaIDispLinkFrequency" = "4"
 	# Not disconnected/enumerable