ARM: 8229/1: sa1100: replace irq numbers with names in irq driver

In preparation for further changes replace direct IRQ numbers with
pre-defined names. This imposes no real code changes.

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>