usb: dwc3: meson-g12a: refactor usb2 phy init

usb: dwc3: meson-g12a: refactor usb2 phy init

Refactor the USB2 PHY init code patch to handle the Amlogic GXL/GXM
not having the PHY mode control registers in the Glue but in the PHY
registers.

The Amlogic GXL/GXM will call phy_set_mode() instead of programming the
PHY mode control registers, thus add two new callbacks to the SoC match
data.

Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>