ARM: S3C64XX: Add usb otg phy control

This patch supports to control usb otg phy of S3C64XX. Currently, the
driver for usb otg controls usb otg phy but it can be removed by this
patch.

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
[Rebased on the newest git/kgene/linux-samsung #for-next]
Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Acked-by: Mark Brown<broonie@opensource.wolfsonmicro.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>