usb: phy: ab8500-usb: add platform_device_id table

Add an initial platform_device_id table to the ab8500-usb driver to
allow probing additional variants of the ab8500 family chips.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Maxime Coquelin <maxime.coquelin@st.com>
Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>