usb: irda: cleanup on ir-usb module

General cleanup on ir-usb module. Introduced
a common header that could be used also on
usb gadget framework.

Lot's of cleanups and now using macros from the header
file.

Signed-off-by: Felipe Balbi <me@felipebalbi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>