mb/google/brya/variants/primus: Disable PCIe6

WWAN (fibocom L850-GL) works in USB mode, so turn off PCIe 6.

BUG=b:194861116

Signed-off-by: Malik_Hsu <malik_hsu@wistron.corp-partner.google.com>
Change-Id: Ie04a5bb2af9ce11f57339f460a7f880bfc14b688
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56649
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

src/mainboard/google/brya/variants/primus/overridetree.cb

@@ -168,6 +168,7 @@ chip soc/intel/alderlake
 				device generic 0 on end
 			end
 		end
+		device ref pcie_rp6 off end #PCIE6 WWAN
 		device ref pcie_rp8 on
 			chip soc/intel/common/block/pcie/rtd3
 				register "enable_gpio" = "ACPI_GPIO_OUTPUT_ACTIVE_HIGH(GPP_H13)"