[media] dib8000: In auto-search, try first with partial reception enabled

TV broadcasters generally use partial reception. So, enable it by
default in auto-search mode. The driver will latter detect if the
transmission is on some other mode.

Acked-By: Patrick Boettcher <pboettcher@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>