MAINTAINERS: add Bug entry for Samsung and memory controller drivers

Add a Bug sections, indicating preferred mailing method for bug
reports, to Samsung SoC related entries and memory controller drivers.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220420104708.106738-1-krzysztof.kozlowski@linaro.org

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Signed-off-by: Arnd Bergmann <arnd@arndb.de>