x86: irq: Reserve IRQ9 for ACPI in PIC mode

Reserve IRQ9 which is to be used as SCI interrupt number
for ACPI in PIC mode.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>