V4L/DVB (4646): Misc. changes, DiB3000MC, MT2060

Changed the attach-function of the dib3000mc-driver to return only one
frontend. In case of multiple dib3000-chips on one board, one has to call the
i2c-enumeration manually before.
Added a field to Microtune 2060 config to output the clock to other
tuners/device on a board.

Signed-off-by: Patrick Boettcher <pb@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>