bcma: fix null pointer in bcma_core_pci_irq_ctl

pc could be null if hosttype != BCMA_HOSTTYPE_PCI.
If we are on a device without a pci core this function is called with
pc = null by b43 and brcmsmac. If the host type is PCI we have a pci
core as well and pc can not be null.
Signed-off-by: NHauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/bcma/driver_pci.c

@@ -232,17 +232,19 @@ void __devinit bcma_core_pci_init(struct bcma_drv_pci *pc)
 int bcma_core_pci_irq_ctl(struct bcma_drv_pci *pc, struct bcma_device *core,
 			  bool enable)
 {
-	struct pci_dev *pdev = pc->core->bus->host_pci;
+	struct pci_dev *pdev;
 	u32 coremask, tmp;
 	int err = 0;
 
-	if (core->bus->hosttype != BCMA_HOSTTYPE_PCI) {
+	if (!pc || core->bus->hosttype != BCMA_HOSTTYPE_PCI) {
 		/* This bcma device is not on a PCI host-bus. So the IRQs are
 		 * not routed through the PCI core.
 		 * So we must not enable routing through the PCI core. */
 		goto out;
 	}
 
+	pdev = pc->core->bus->host_pci;
+
 	err = pci_read_config_dword(pdev, BCMA_PCI_IRQMASK, &tmp);
 	if (err)
 		goto out;