This patch starts dis-entangling some of the enumeration logic by
moving initialization code into the usb_alloc_dev() constructor.
Some call signatures changed; a usbcore-internal declaration was
moved in <linux/usb.h> to a more appropriate location.

With the driver model init now more centralized, it's safer to
use driver model calls (including dev_info) a lot earlier, so
the "new device at address N" message now does that.  It also
reports the device speed, which may not be evident otherwise.