V4L/DVB (9576): cx88-dvb: MFE attachment clean-up for HVR-3000/4000

This cleans-up MFE attachment for these cards plus
two cases of potential memory leak on attachment
failure.

Signed-off-by: Darron Broad <darron@kewl.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>