ARM: EXYNOS4: Add usb host phy control

EXYNOS4 has 2 phys for usb host and usb device. This patch supports to
control usb host phy of EXYNOS4.

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>