[media] Use smaller i2c transaction size with 18271 tuner

Configure the tda18271 to use a smaller transaction size by default, which
works around some sort of i2c bug in the Polaris driver (which needs to be
debugged).

This should be safe for other boards (being in tuner-core means it will be
enabled by default), although testing needs to be done.

Signed-off-by: Devin Heitmueller <dheitmueller@hauppauge.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>