ARM: MAINTAINERS: drop empty entries for removed boards

Drop empty and redundant maintainer entries for boards which were
removed to fix `scripts/get_maintainer.pl --self-test=sections` errors
like:

  ./MAINTAINERS:2021: warning: section without file pattern	ARM/CIRRUS LOGIC EDB9315A MACHINE SUPPORT

[arnd: only remove the obviously stale ones for now]

Cc: Lennert Buytenhek <kernel@wantstofly.org>
Cc: Steve Sakoman <sakoman@gmail.com>
Cc: Mark F. Brown <mark.brown314@gmail.com>
Cc: Robert Jarzmik <robert.jarzmik@free.fr>
Cc: Florian Fainelli <florian@openwrt.org>
Cc: Simtec Linux Team <linux@simtec.co.uk>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20231218134532.50599-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>