lib: utils/irqchip: fix typo when checking for CPU node

Fix typo in irqchip_imsic_update_hartid_table() when checking for CPU
node.

Signed-off-by: Jan Remes <jan.remes@codasip.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>