mn10300/PCI: Remove useless pcibios_last_bus

pcibios_last_bus was apparently copied from x86.  On mn10300, it is
statically initialized to -1 and may be set with the "pci=lastbus=<X>"
boot option, but it is never tested.  This patch removes everything
related to pcibios_last_bus.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

arch/mn10300/unit-asb2305/pci-asb2305.h

@@ -35,7 +35,6 @@ extern void pcibios_resource_survey(void);
 
 /* pci.c */
 
-extern int pcibios_last_bus;
 extern struct pci_ops *pci_root_ops;
 
 extern struct irq_routing_table *pcibios_get_irq_routing_table(void);

arch/mn10300/unit-asb2305/pci.c

@@ -24,7 +24,6 @@
 
 unsigned int pci_probe = 1;
 
-int pcibios_last_bus = -1;
 struct pci_ops *pci_root_ops;
 
 /*
@@ -392,10 +391,6 @@ char *__init pcibios_setup(char *str)
 	if (!strcmp(str, "off")) {
 		pci_probe = 0;
 		return NULL;
-
-	} else if (!strncmp(str, "lastbus=", 8)) {
-		pcibios_last_bus = simple_strtol(str+8, NULL, 0);
-		return NULL;
 	}
 
 	return str;