irqchip/ti-sci-inta: Remove dead code in ti_sci_inta_set_type()

In the function ti_sci_inta_set_type(), the statement "return -EINVAL;"
out of switch case is dead code, remove it.

Fixes: 9f1463b8 ("irqchip/ti-sci-inta: Add support for Interrupt Aggregator driver")
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Link: https://lore.kernel.org/r/1591437017-5295-1-git-send-email-yangtiezhu@loongson.cn