ARM: dts: correct the usb phy node in exynos5420-peach-pit

The vbus-supply property is wrongly updated in the
usbdrd node instead of the usbdrd_phy node. This patch
fixes the same.

Signed-off-by: Arun Kumar K <arun.kk@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>