MAINTAINERS: ARM: axm: add Krzysztof Kozlowski as maintainer

MAINTAINERS: ARM: axm: add Krzysztof Kozlowski as maintainer

There is no maintainers entry for the ARM LSI AXM 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 AXM but I can take odd fixes
now and then.

Link: https://lore.kernel.org/r/20240613134910.7862-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>