MAINTAINERS: Add entry for Maxim chargers on Samsung boards

Add myself as supporter to help in reviewing patches for Maxim 14577 and
77693 MUIC charger drivers. These are used on Exynos-based boards
(Trats 2, Gear 1 and Gear 2).

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Acked-By: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Sebastian Reichel <sre@kernel.org>