mb/lenovo/x60: Fix devicetree hierarchy

The Ricoh bridge device is actually on the external PCI bus. To make the
driver configuration usable, also add a PCI device below it.

Change-Id: I58a25da9d676a19b47e8b88438152bc247c024b4
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57474
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/lenovo/x60/devicetree.cb

@@ -89,7 +89,11 @@ chip northbridge/intel/i945
 			device pci 1d.7 on # USB2 EHCI
 				subsystemid 0x17aa 0x200b
 			end
-			device pci 1e.0 on end # PCI Bridge
+			device pci 1e.0 on # PCI Bridge
+				chip southbridge/ricoh/rl5c476
+					device pci 0.0 on end
+				end
+			end
 			device pci 1e.2 off end # AC'97 Audio
 			device pci 1e.3 off end # AC'97 Modem
 			device pci 1f.0 on # PCI-LPC bridge
@@ -209,7 +213,5 @@ chip northbridge/intel/i945
 				end
 			end
 		end
-		chip southbridge/ricoh/rl5c476
-		end
 	end
 end