ARM: 8230/1: sa1100: shift IRQs by one

As IRQ0 should not be used (especially in when using irq domains), shift all
virtual IRQ numbers by one.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>