irqchip/ti-sci-inta: Use ERR_CAST inlined function instead of ERR_PTR(PTR_ERR(...))

A coccicheck run provided information like the following.

drivers/irqchip/irq-ti-sci-inta.c:250:9-16: WARNING: ERR_CAST can be used
with vint_desc.

Generated by: scripts/coccinelle/api/err_cast.cocci

Thus adjust the exception handling in one if branch.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Link: https://lore.kernel.org/r/776b7135-26af-df7d-c3a9-4339f7bf1f15@web.de

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

@@ -246,8 +246,8 @@ static struct ti_sci_inta_event_desc *ti_sci_inta_alloc_irq(struct irq_domain *d
 	/* No free bits available. Allocate a new vint */
 	vint_desc = ti_sci_inta_alloc_parent_irq(domain);
 	if (IS_ERR(vint_desc)) {
-		mutex_unlock(&inta->vint_mutex);
-		return ERR_PTR(PTR_ERR(vint_desc));
+		event_desc = ERR_CAST(vint_desc);
+		goto unlock;
 	}
 
 	free_bit = find_first_zero_bit(vint_desc->event_map,
@@ -259,6 +259,7 @@ static struct ti_sci_inta_event_desc *ti_sci_inta_alloc_irq(struct irq_domain *d
 	if (IS_ERR(event_desc))
 		clear_bit(free_bit, vint_desc->event_map);
 
+unlock:
 	mutex_unlock(&inta->vint_mutex);
 	return event_desc;
 }