USB: iuu_phoenix: fix sysfs-attribute creation

Make sure sysfs attributes are created at port probe.

A recent patch ("USB: iuu_phoenix: fix port-data memory leak") removed
the sysfs-attribute creation by mistake.

Reported-by: Yuanhan Liu <yuanhan.liu@intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>