media: dvb_frontend: move algo-specific settings to a function

As we're planning to call this code from somewhere else,
let's first move it to its own function.

Link: https://lore.kernel.org/linux-media/daa69edd80e7fcf979062273f3067cb7b5573d52.1592419750.git.mchehab+huawei@kernel.org


Reviewed-by: Marc Gonzalez <marc.w.gonzalez@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>