irqchip/renesas-rza1: Fix an use-after-free in rza1_irqc_probe()

The gic_node is still being used in the rza1_irqc_parse_map() call
after the of_node_put() call, which may result in use-after-free.

Fixes: a644ccb8 ("irqchip: Add Renesas RZ/A1 Interrupt Controller driver")
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Marc Zyngier <maz@kernel.org>