base: power: Add generic OF-based power domain look-up

base: power: Add generic OF-based power domain look-up

This patch introduces generic code to perform power domain look-up using
device tree and automatically bind devices to their power domains.
Generic device tree binding is introduced to specify power domains of
devices in their device tree nodes.

Backwards compatibility with legacy Samsung-specific power domain
bindings is provided, but for now the new code is not compiled when
CONFIG_ARCH_EXYNOS is selected to avoid collision with legacy code. This
will change as soon as Exynos power domain code gets converted to use
the generic framework in further patch.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Reviewed-by: Mark Brown <broonie@linaro.org>
Reviewed-by: Kevin Hilman <khilman@linaro.org>
Reviewed-by: Philipp Zabel <philipp.zabel@gmail.com>
[on i.MX6 GK802]
Tested-by: Philipp Zabel <philipp.zabel@gmail.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
[shawn.guo: http://thread.gmane.org/gmane.linux.kernel.samsung-soc/31029]
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>