USB: rename the usb misc class from "usb" to "usbmisc"

This class was not named properly years ago, and it turns out that tools
like udev can't properly see the devices in this class after booting due
to the fact that there is a bus with the same name in the system.

Changing this to "usbmisc" fixes this problem, and it solves the problem
for the future when we want to unify classes and busses.

Reported-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>