MAINTAINERS: adjust ARM/INTEL IXP4XX ARM ARCHITECTURE to ixp4xx clean-up

MAINTAINERS: adjust ARM/INTEL IXP4XX ARM ARCHITECTURE to ixp4xx clean-up

Commit c83227a5d05e ("irq/gpio: ixp4xx: Drop boardfile probe path") and
commit 155e4306107f ("clocksource/drivers/ixp4xx: Drop boardfile probe
path") remove files include/linux/irqchip/irq-ixp4xx.h and
include/linux/platform_data/timer-ixp4xx.h, but miss to adjust MAINTAINERS.

Hence, ./scripts/get_maintainer.pl --self-test=patterns complains about
broken references.

Remove file entries for those files in ARM/INTEL IXP4XX ARM ARCHITECTURE.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20221115123102.22732-1-lukas.bulwahn@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>