ARM: EXYNOS: Remove legacy power domain registration code

This patch removes static definitions of power domains and code
responsible for registering them and adding devices to them, since only
DT based boot is now supported on Exynos.

Cc: linux-pm@vger.kernel.org
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>