USB: ftdi_sio: Handle FT232RL devices like FT232BM devices

Handle the FT232RL device type in exactly the same way as FT232BM
devices (FT232RL detection was added around kernel 2.6.20 but not code
for handling it).

Signed-off-by: Andrew M. Bishop <amb@gedanken.demon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>