Enable usb0 in all boot phases for use with DFU

Signed-off-by: Sjoerd Simons <sjoerd@collabora.com>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Signed-off-by: Martyn Welch <martyn.welch@collabora.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>