system76/rpl: Add discrete thunderbolt driver to bonw15, serw13

Change-Id: I9545fa5b46220a2487d5ca09bb8a074a460e420a

src/mainboard/system76/rpl/variants/bonw15/overridetree.cb

@@ -91,6 +91,9 @@ chip soc/intel/alderlake
 				.clk_req = 15,
 				.flags = PCIE_RP_HOTPLUG | PCIE_RP_LTR,
 			}"
+			chip drivers/intel/dtbt
+				device pci 00.0 on end
+			end
 		end
 
 		device ref pcie_rp21 on

src/mainboard/system76/rpl/variants/serw13/overridetree.cb

@@ -101,6 +101,9 @@ chip soc/intel/alderlake
 				.clk_req = 15,
 				.flags = PCIE_RP_HOTPLUG | PCIE_RP_LTR,
 			}"
+			chip drivers/intel/dtbt
+				device pci 00.0 on end
+			end
 		end
 	end
 end