fpga: altera-cvp: fix 'bad IO access' on x86_64

If mapping the CvP BAR fails, we still can configure the FPGA via
PCI config space access. In this case the iomap pointer is NULL.
On x86_64, passing NULL address to pci_iounmap() generates
"Bad IO access at port 0x0" output with stack call trace. Fix it.
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Acked-by: Alan Tull <atull@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/fpga/altera-cvp.c

@@ -477,6 +477,7 @@ static int altera_cvp_probe(struct pci_dev *pdev,
 	return 0;
 
 err_unmap:
+	if (conf->map)
 		pci_iounmap(pdev, conf->map);
 	pci_release_region(pdev, CVP_BAR);
 err_disable:
@@ -493,6 +494,7 @@ static void altera_cvp_remove(struct pci_dev *pdev)
 
 	driver_remove_file(&altera_cvp_driver.driver, &driver_attr_chkcfg);
 	fpga_mgr_unregister(mgr);
+	if (conf->map)
 		pci_iounmap(pdev, conf->map);
 	pci_release_region(pdev, CVP_BAR);
 	pci_read_config_word(pdev, PCI_COMMAND, &cmd);