p54usb: bring first generation devices back to life

This patch fixes a serious regression (introduced by:
"p54: fix memory management")
that affected isl3886+net2280 usb devices operation.

Signed-off-by: Christian Lamparter <chunkeey@web.de>
Tested-by: Artur Skawina <art.08.09@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>