MAINTAINERS: pinctrl: samsung: Add two new maintainers

Extend the list of maintainers for Samsung pinctrl driver with Sylwester
and Krzysztof.

Cc: Kukjin Kim <kgene@kernel.org>
Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Tomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>