media: ddbridge: move CI detach code to ddbridge-ci.c

Move the CI teardown code to ddbridge-ci.c where everything else related
to CI hardware lives.

Cc: Ralph Metzler <rjkm@metzlerbros.de>
Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>