usbmode: add config #0 and delay before actual config

usbmode: add config #0 and delay before actual config

I have a Huawei ME909s-120.  When I switch directly from configuration
to go via configuration #0, and a short delay, and then to configuration
well. So in order to fix it, add config #0 and a 100milliseconds
delay before switching to actual config, like in USB_ModeSwitch.

References: https://www.draisberghof.de/usb_modeswitch/bb/viewtopic.php?f=4&t=2710&sid=505ed44b4064fef7009f0c26aac085e2&start=15
Signed-off-by: Henrik Ginstmark <henrik@ginstmark.se>
Signed-off-by: Petr Štetiar <ynezz@true.cz> [rebased, commit description facelift]