mb/google/skyrim: Enable USB controllers in devicetree

BUG=b:214413631
TEST=builds

Signed-off-by: Jon Murphy <jpmurphy@google.com>
Change-Id: I9ca2c16d97e064b32400356e1de37f3f70155a07
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62152
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/skyrim/variants/baseboard/devicetree.cb

@@ -8,6 +8,10 @@ chip soc/amd/sabrina
 		end
 		device ref gpp_bridge_a on  # Internal GPP Bridge 0 to Bus A
 			device ref gfx on end # Internal GPU (GFX)
+			device ref xhci_0 on
+			end
+			device ref xhci_1 on
+			end
 		end
 	end # domain
 	device ref uart_0 on end # UART0