dwc2: use the nonblock argument in submit_int_msg

An USB 1.1 keyboard connected to dwc2 through a high-speed hub does not
report status until it changes. With this patch you can enable keyboard
by pressing a key while USB devices are probed. Without a keypress no
state is reported and the probe times out. We don't want to wait for a
keypress or timeout while polling for keypresses so implement an int_msg
nonblock variant that exits early on error.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>