mpc83xx: Introduce ARCH_MPC834*

Replace CONFIG_MPC834* with proper CONFIG_ARCH_MPC834* Kconfig options.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/drivers/pci/pci_auto.c b/drivers/pci/pci_auto.c
index d7237f6..a673d8a 100644
--- a/drivers/pci/pci_auto.c
+++ b/drivers/pci/pci_auto.c
@@ -359,7 +359,7 @@
 		      PCI_DEV(dm_pci_get_bdf(dev)));
 		break;
 #endif
-#if defined(CONFIG_MPC834x) && !defined(CONFIG_VME8349)
+#if defined(CONFIG_ARCH_MPC834X) && !defined(CONFIG_VME8349)
 	case PCI_CLASS_BRIDGE_OTHER:
 		/*
 		 * The host/PCI bridge 1 seems broken in 8349 - it presents