media: em28xx: Enable inversion for Solo/Dual HD DVB models

Hauppauge Solo/Dual HD DVB models use a si2157 tuner, which is set to
produce inverted spectrum. This configures the si2168 DVB demod for
inverted spectrum on both affected models.

[mchehab@s-opensource.com: rebased on the top of upstream]
Signed-off-by: Brad Love <brad@nextdimension.cc>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>