phy: usb: Restructure in preparation for adding 7216 USB support

The driver is being restructured in preparation for adding support
for the new Synopsys USB conroller on the 7216. Since all the bugs
and work-arounds in previous STB chips are supposed to be fixed,
most of the code in phy-brcm-usb-init.c is not needed. Instead of
adding more complexity to the already complicated phy-brcm-usb-init.c
module, the driver will be restructured to use a vector table to
dispatch into different C modules for the different controllers.

There was also some general cleanup done including some ipp setup
code that was incorrect.

Signed-off-by: Al Cooper <alcooperx@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>