phy: exynos5-usbdrd: Fix phy calibration for platform other than 5420

PHY calibration is required only on Exynos5420 based systems.
Exynos5250 and other Exynos SoCs using this DRD PHY don't need it.

This change will be squashed with earlier patch:
phy: exynos5-usbdrd: Calibrate LOS levels for exynos5420/5800

Signed-off-by: Vivek Gautam <gautam.vivek@samsung.com>