irqchip/ti-sci-inta: Fix kernel crash if irq_create_fwspec_mapping fail

irq_create_fwspec_mapping() can fail, returning 0 as parent_virq. In this
case vint_desc is going to be NULL in ti_sci_inta_alloc_irq() which will
cause NULL pointer dereference.

Also note that irq_create_fwspec_mapping() returns 'unsigned int' so the
check '<=' was wrong.

Use -EINVAL if irq_create_fwspec_mapping() returned with 0.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

drivers/irqchip/irq-ti-sci-inta.c

@@ -159,9 +159,9 @@ static struct ti_sci_inta_vint_desc *ti_sci_inta_alloc_parent_irq(struct irq_dom
 	parent_fwspec.param[1] = vint_desc->vint_id;
 
 	parent_virq = irq_create_fwspec_mapping(&parent_fwspec);
-	if (parent_virq <= 0) {
+	if (parent_virq == 0) {
 		kfree(vint_desc);
-		return ERR_PTR(parent_virq);
+		return ERR_PTR(-EINVAL);
 	}
 	vint_desc->parent_virq = parent_virq;