rt2x00pci: Disable memory-write-invalidate when the driver exits

The driver calls pci_set_mwi to enable memory-write-invalidate when it
is initialized, but does not call pci_clear_mwi when it is removed. Many
other drivers calls pci_clear_mwi when pci_set_mwi is called, such as
r8169, 8139cp and e1000.

This patch adds pci_clear_mwi in error handling and removal procedure,
which can fix the problem.

Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
Acked-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ralink/rt2x00/rt2x00pci.c

@@ -149,6 +149,7 @@ exit_free_device:
 	ieee80211_free_hw(hw);
 
 exit_release_regions:
+	pci_clear_mwi(pci_dev);
 	pci_release_regions(pci_dev);
 
 exit_disable_device:
@@ -173,6 +174,7 @@ void rt2x00pci_remove(struct pci_dev *pci_dev)
 	/*
 	 * Free the PCI device data.
 	 */
+	pci_clear_mwi(pci_dev);
 	pci_disable_device(pci_dev);
 	pci_release_regions(pci_dev);
 }