uboot-imx

usb: dwc2: Call board_usb_init() from usb_lowlevel_init()

This patch makes the dwc2 controller like ehci / ohci / xhci controllers
by calling the board_usb_init() function from usb_lowlevel_init.

This can then be implemented by specific platforms to initialise
their USB hardware (phys / clocks etc).

Signed-off-by: Peter Griffin <peter.griffin@linaro.org>