rtl818x: pci_iomap() should pair with pci_iounmap()

Currently the driver uses pci_iomap() but iounmap() is called in
the error path

Change to use pci_iounmap() instead.

Reported-by: Huqiu Liu <liuhq11@mails.tsinghua.edu.cn>
Signed-off-by: Andrea Merello <andrea.merello@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rtl818x/rtl8180/dev.c b/drivers/net/wireless/rtl818x/rtl8180/dev.c
index 470a1e3..bf59ff9 100644
--- a/drivers/net/wireless/rtl818x/rtl8180/dev.c
+++ b/drivers/net/wireless/rtl818x/rtl8180/dev.c
@@ -1137,7 +1137,7 @@
 	return 0;
 
  err_iounmap:
-	iounmap(priv->map);
+	pci_iounmap(pdev, priv->map);
 
  err_free_dev:
 	ieee80211_free_hw(dev);