poplar: add DWC2 OTG gadget support

It enables DWC2 OTG gadget driver support for Poplar board.  As
usb2_phy_init() is being always called from board_init(), we can save
the call from board_usb_init().

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
2 files changed