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