ARM: EXYNOS: Remove leftovers of the Samsung specific power domain control

Nowadays we use generic power domain support instead of Samsung
specific power domain control driver.

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