V4L/DVB (13081): saa7134: use the #define for the xc5000 radio_input field

Dmitri's patch for the Behold X7 didn't use the #define I had setup for
XC5000_RADIO_FM1, so cut over to using that instead of "1".

Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>