V4L/DVB (11964): b2c2: Fix problems with frontend attachment

The frontend attachment code didn't handle cases where the frontend
partially failed to attach.  For instance, when the demod was attached
successfully but the tuner driver wasn't compiled or fails to init for some
reason.  In these cases we try to clean up the partial attachment and fail
instead of proceeding with a broken frontend.

If frontend registration fails, clean up with dvb_frontend_detach() rather
than just calling the frontend's main release method.  The former does some
additional stuff, like release an attached tuner and take care of putting
symbols when dynamic binding is used.

In skystar2_rev23_attach() it's not necessary to set fc->dev_type, that
gets set before skystar2_rev23_attach() is called.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Patrick Boettcher <pboettcher@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>