Port USB firmware update to stm32f4 dwc usb from st usb.
This includes usb dwc usb stream inplementation, generic
endpoint interfaces, and the sweetberry test case.
BUG=chromium:608039
TEST=usb update works
BRANCH=None
Change-Id: Ia26e4f7e990ee64991468799c99b036f5f32190f
Signed-off-by: Nick Sanders <nsanders@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/377520
Reviewed-by: Randall Spangler <rspangler@chromium.org>