MAINTAINERS: Add entry for Samsung SoC clock drivers

This patch adds an entry for Samsung SoC clock drivers located under
drivers/clk/samsung/ directory, with me taking the maintainer role.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Mike Turquette <mturquette@linaro.org>
Acked-by: Sachin Kamat <sachin.kamat@linaro.org>
Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>