V4L/DVB (5960): Add module parameter to enable SFN workaround

In some areas in the world the broadcasters are not using the same
cellid for each transmitter in a SFN. The DiBcom has problems with
that setup. The module parameter buggy_sfn_workaround makes it re-usable.

Signed-off-by: Matt Doran <matt.doran@papercut.biz>
Signed-off-by: Patrick Boettcher <pb@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>