usb3/phy: Fix to identify USB3 port

Since virual address could be shifted if certain driver is added or removed,
would be better to use physical address. 0x12100000 is dedicated for USB3
port0 and 0x12500000 is dedicated for port1 according to exynos5422.dtsi and
its datasheet.

Change-Id: I451a2b50a41962131dcf1efe710cf6f1e66edaba
Signed-off-by: Dongjin Kim <tobetter@gmail.com>