iommu/exynos: Remove dbgname from drvdata of a System MMU

This patch removes dbgname member from sysmmu_drvdata structure.
Kernel message for debugging already has the name of a single
System MMU node. It also removes some compilation warnings.

Signed-off-by: Cho KyongHo <pullip.cho@samsung.com>
Signed-off-by: Shaik Ameer Basha <shaik.ameer@samsung.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>