V4L/DVB (6229): dvb-pll: increase DVB_PLL_MAX to 64

Increased DVB_PLL_MAX from 16 to a figure that would never be reached in a
practical sense.

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