[media] em28xx-dvb: remove one level of identation at fini callback

Simplify the logic a little by removing one level of identation.
Also, it only makes sense to print something if the .fini callback
is actually doing something.

Reviewed-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>