[media] stb0899: enable auto inversion handling unconditionally

It seems that current inversion handling addresses only the signal
routing on the PCB, i. e. IQ signals are either swapped or not.
But when the device is operated in a Satellite Channel Router (SCR)
environment, an additional inversion is required due to the way how
the SCR works. Therefore it makes sense to me to always enable auto
inversion handling and drop the enum value IQ_SWAP_AUTO.

Signed-off-by: Reinhard Nißl <rnissl@gmx.de>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>