ahci: always fall back to single-MSI mode

Don't try to guess what the errors from pci_irq_alloc_vectors mean, as
that's too fragile.  Instead always try allocating a single vector
when multi-MSI mode fails.  This makes various intel Desktop and
Laptop CPUs use MSI again.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Michael Marley <michael@michaelmarley.com>
Tested-by: Michael Marley <michael@michaelmarley.com>
Fixes: 0b9e298 ("ahci: use pci_alloc_irq_vectors")
Signed-off-by: Tejun Heo <tj@kernel.org>

Author: Christoph Hellwig

drivers/ata/ahci.c

@@ -1436,13 +1436,6 @@ static int ahci_init_msi(struct pci_dev *pdev, unsigned int n_ports,
 				"ahci: MRSM is on, fallback to single MSI\n");
 			pci_free_irq_vectors(pdev);
 		}
-
-		/*
-		 * -ENOSPC indicated we don't have enough vectors.  Don't bother
-		 * trying a single vectors for any other error:
-		 */
-		if (nvec < 0 && nvec != -ENOSPC)
-			return nvec;
 	}
 
 	/*