iommu/exynos: support for device tree

This commit adds device tree support for System MMU. This also include the following changes and enhancements:

* use managed device helper functions.
Simplyfies System MMU device driver.

* use only a single clock descriptor.
System MMU device descriptor is seperate if it is imposible to make a single clock descriptor to make a device descriptor for a group of System MMUs.

* removed dbgname member from sysmmu_drvdata structure. debugging kernel message for a System MMU is distinguisheable with the name of device descroptors.

---
 drivers/iommu/Kconfig        |    5 +-
 drivers/iommu/exynos-iommu.c |  192 ++++++++++++++++++------------------------
 2 files changed, 83 insertions(+), 114 deletions(-)

index c332fb9..d45f3c9 100644
@@ -168,16 +168,15 @@ config TEGRA_IOMMU_SMMU
 
 config EXYNOS_IOMMU
 	bool "Exynos IOMMU Support"
-	depends on ARCH_EXYNOS && EXYNOS_DEV_SYSMMU
+	depends on ARCH_EXYNOS
 	select IOMMU_API
+	default n
 	help
 	  Support for the IOMMU(System MMU) of Samsung Exynos application
 	  processor family. This enables H/W multimedia accellerators to see
 	  non-linear physical memory chunks as a linear memory in their
 	  address spaces
 
-	  If unsure, say N here.
-
 config EXYNOS_IOMMU_DEBUG
 	bool "Debugging log for Exynos IOMMU"
 	depends on EXYNOS_IOMMU

1.7.2.5