irqchip/alpine-msi: Fix freeing of interrupts on allocation error path

The alpine-msi driver has an interesting allocation error handling,
where it frees the same interrupts repeatedly. Hilarity follows.

This code is probably never executed, but let's fix it nonetheless.

Fixes: e6b78f2c ("irqchip: Add the Alpine MSIX interrupt controller")
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Antoine Tenart <atenart@kernel.org>
Cc: Tsahee Zidenberg <tsahee@annapurnalabs.com>
Cc: Antoine Tenart <atenart@kernel.org>
Link: https://lore.kernel.org/r/20201129135525.396671-1-maz@kernel.org

drivers/irqchip/irq-alpine-msi.c

@@ -165,8 +165,7 @@ static int alpine_msix_middle_domain_alloc(struct irq_domain *domain,
 	return 0;
 
 err_sgi:
-	while (--i >= 0)
-		irq_domain_free_irqs_parent(domain, virq, i);
+	irq_domain_free_irqs_parent(domain, virq, i - 1);
 	alpine_msix_free_sgi(priv, sgi, nr_irqs);
 	return err;
 }