ASoC: samsung: Add the DT binding files entry to MAINTAINERS

This patch adds missing DT binding files to the Samsung ASoC
drivers entry.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>