iommu/exynos: Add Maintainers entry for Exynos SYSMMU driver

Add Marek Szyprowski as maintainer for Exynos IOMMU driver.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>