MAINTAINERS: Add myself as Samsung SoC clock drivers co-maintainer

Add myself to the SAMSUNG SOC CLOCK DRIVERS entry, I'm going to review
and test related patches as supporter.  I can access all the datasheet
of Exynos SoC series and can do tests on Exynos based boards.  I have
implemented the exynos4415/5433 clock drivers and co-authored the
exynos3250 clock driver.  While at it, add missing paths of the exynos
clock driver files.

Cc: Tomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>