V4L/DVB (7360): tuner-simple: fix return value of simple_dvb_configure

simple_dvb_configure returns the actual tuned frequency to its caller, so
it must be declared as a u32 rather than an int.  As a result, we will
return 0 to indicate a failure.

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>