V4L/DVB (5991): dvb-pll: Set minimum and maximum frequency properly

The tuner maximum frequency wasn't being set, while the minimum 
frequency was set to what the maximum should have been.

If a future patch were to enforce these limits, dvb-pll would be 
effectively broken.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>