MAINTAINERS: ARM: alphascale: add Krzysztof Kozlowski as maintainer

MAINTAINERS: ARM: alphascale: add Krzysztof Kozlowski as maintainer

Apparently there was never a maintainers entry for the ARM Alphascale
ASM9260 SoC, thus patches end up nowhere.  Add such entry, because even
if platform is orphaned and on its way out of the kernel, it is nice to
take patches if someone sends something.

I do not plan to actively support/maintain ARM Alphascale but I can take
odd fixes now and then.

Cc: Oleksij Rempel <linux@rempel-privat.de>
Link: https://lore.kernel.org/r/20240612141018.7348-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>