usb: gadget: udc: lpc32xx: add support for stotg04 phy

The STOTG04 phy is used as a drop-in replacement of the ISP1301 but some
bits doesn't have exactly the same meaning and this can lead to issues.
Detect the phy dynamically and avoid writing to reserved bits.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>