V4L/DVB (9316): s5h1411: Power down s5h1411 when not in use

Power down the s5h1411 demodulator when not in use (on the Pinnacle 801e, this
brings idle power from 123ma down to 84ma).

Signed-off-by: Devin Heitmueller <devin.heitmueller@gmail.com>
Acked-by: Steven Toth <stoth@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>