Start with a short USB hub reset delay of 20ms. This can be enough for
some configurations. Switch to longer reset delay only if the short
delay hasn't been long enough.

This USB hub reset handling strategy is also used in the Linux kernel
USB hub driver, function hub_port_reset().

Without patch:

    $ time usb
    usb: USB: scanning bus for devices...
    usb: 17 USB Device(s) found
    time: 21750ms

With patch:

    $ time usb
    usb: USB: scanning bus for devices...
    usb: 17 USB Device(s) found
    time: 16355ms

Delta: ~5.5 seconds

Signed-off-by: Primoz Fiser <primoz.fiser@norik.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>