MAINTAINERS: add reviewer entry for Samsung/Exynos platform

Adds myself as reviewer for Samsung/Exynos platform to help
in review of current and upcoming SoCs patches.

Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Link: https://lore.kernel.org/r/20220105164341.27479-1-alim.akhtar@samsung.com


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>