irqchip/renesas-rza1: Prevent 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>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lkml.kernel.org/r/1562566745-7447-3-git-send-email-wen.yang99@zte.com.cn