Used synthesizer is very typical integer-N PLL, with configurable
reference frequency divider, output frequency divider and of
course N itself. Most common method to calculate values is first
select output divider, then calculate VCO frequency and finally
calculate PLL N from VCO frequency. Do it that way.

Also make some cleanups for filter logic and signal strength.
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>