configs: sunxi: Drop CONFIG_SUNXI_USB_PHYS

Now number of PHY on Allwinner is handling via dt data,
drivers at phy/allwinner/phy-sun4i-usb.c

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com>