MAINTAINERS: Add new Samsung subsystems

Add next Samsung subsystems with Sam Protsenko as a maintainer:

- Samsung CCF Clock Framework
- Exynos850 SoC Support
- Samsung SoC Drivers

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>