mb/google/octopus/variants: Disable xHCI compliance mode for Fleex

Some usb devices exhibits signal loss which causes xHCI entering
compliance mode. The resolution is to disable xHCI compliance mode.

BRANCH=octopus
BUG=b:120009029
TEST=Verified usb operation successfully.

Change-Id: Ic7fa08c894397598dee3c4ff9a764e43383a0627
Signed-off-by: Amanda Huang <amanda_hwang@compal.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/30984
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Justin TerAvest <teravest@chromium.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

src/mainboard/google/octopus/variants/fleex/overridetree.cb

@@ -140,4 +140,7 @@ chip soc/intel/apollolake
 			end
 		end	# - I2C 7
 	end
+
+	# Disable compliance mode
+	register "DisableComplianceMode" = "1"
 end