usb: ehci-s5p: skip phy setup for Exynos5440 based platforms

Exynos5440 does not require any explict USB phy configuration. So skip
the USB phy configuration for Exynos5440 based platforms.

Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
Ackked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>