PCI/msi: fix the pci_alloc_irq_vectors_affinity stub

We need to return an error for any call that asks for MSI / MSI-X
vectors only, so that non-trivial fallback logic can work properly.

Also valid dev->irq and use the "correct" errno value based on feedback
from Linus.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Fixes: aff17164 ("PCI: Provide sensible IRQ vector alloc/free routines")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/pci.h

@@ -1342,9 +1342,9 @@ pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
 			       unsigned int max_vecs, unsigned int flags,
 			       const struct irq_affinity *aff_desc)
 {
-	if (min_vecs > 1)
-		return -EINVAL;
+	if ((flags & PCI_IRQ_LEGACY) && min_vecs == 1 && dev->irq)
 		return 1;
+	return -ENOSPC;
 }
 
 static inline void pci_free_irq_vectors(struct pci_dev *dev)