Revert "rt2x00pci: Use PCI MSIs whenever possible"

This reverts commit 9483f40d.

Some devices stop to connect with above commit, see:
https://bugzilla.kernel.org/show_bug.cgi?id=61621

Since there is no clear benefit of having MSI enabled, just revert
change to fix the problem.

Cc: stable@vger.kernel.org # 3.11+
Signed-off-by: NStanislaw Gruszka <sgruszka@redhat.com>
Acked-by: NJakub Kicinski <kubakici@wp.pl>
Acked-by: NGertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2x00pci.c

@@ -105,13 +105,11 @@ int rt2x00pci_probe(struct pci_dev *pci_dev, const struct rt2x00_ops *ops)
 		goto exit_release_regions;
 	}
 
-	pci_enable_msi(pci_dev);
-
 	hw = ieee80211_alloc_hw(sizeof(struct rt2x00_dev), ops->hw);
 	if (!hw) {
 		rt2x00_probe_err("Failed to allocate hardware\n");
 		retval = -ENOMEM;
-		goto exit_disable_msi;
+		goto exit_release_regions;
 	}
 
 	pci_set_drvdata(pci_dev, hw);
@@ -152,9 +150,6 @@ int rt2x00pci_probe(struct pci_dev *pci_dev, const struct rt2x00_ops *ops)
 exit_free_device:
 	ieee80211_free_hw(hw);
 
-exit_disable_msi:
-	pci_disable_msi(pci_dev);
-
 exit_release_regions:
 	pci_release_regions(pci_dev);
 
@@ -179,8 +174,6 @@ void rt2x00pci_remove(struct pci_dev *pci_dev)
 	rt2x00pci_free_reg(rt2x00dev);
 	ieee80211_free_hw(hw);
 
-	pci_disable_msi(pci_dev);
-
 	/*
 	 * Free the PCI device data.
 	 */