Add support for generic power domain for Exynos4 platforms and remove the
Samsung specific power domain control for Exynos4.

The generic power domain infrastructure is used to control the power domains
available on Exynos4. For non-dt platforms, the power domains are statically
instantiated. For dt platforms, the power domain nodes found in the device
tree are instantiated.

Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>