[media] as102: set optimal eLNA config values for each device

Ryley and me tested several eLNA configuration values with both a rooftop
and a portable antenna.

Ryley fuond out that the best value for his Elgato stick is indeed the current
default value 0xC0.

Instead, my stick is not capable of tuning VHF channels with 0xC0. With 0x80,
VHF works but the tuner sensitivity with the portable antenna is poor.
Instead, the value 0xA0 works with VHF and also gives good performance with
both the rooftop and the portable antenna.

So we concluded that devices built on the reference design work best with 0xA0,
while custom designs (Elgato, PCTV) seem to require 0xC0.

I also removed the unused parameter "minor" in struct as102_dev_t.

Signed-off-by: Gianluca Gennari <gennarone@gmail.com>
Signed-off-by: Ryley Angus <rangus@student.unimelb.edu.au>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>