media: dvb-pll: don't re-validate tuner frequencies

The dvb_frontend core already checks for the frequencies. No
need for any additional check inside the driver.

It is part of the fixes for the following bug:
  https://bugzilla.opensuse.org/show_bug.cgi?id=1116374

Fixes: a3f90c75

 ("media: dvb: convert tuner_info frequencies to Hz")
Reported-by: Stakanov Schufter <stakanov@eclipso.eu>
Reported-by: Takashi Iwai <tiwai@suse.de>
Cc: stable@vger.kernel.org # For 4.19
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>