staging: ozwpan: Increase farewell report size.

Farewell report size can be bigger than one byte, increase array
size to accomodate maximum 32 bytes of farewell report.

Signed-off-by: Rupesh Gujare <rupesh.gujare@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>