forked from Mirrors/opensbi

Interrupt source 0 is reserved. Hence the irq should start from 1.
Fixes: 2b79b694a8
("lib: irqchip/plic: Add priority save/restore helpers")
Signed-off-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Anup Patel <anup@brainfault.org>