[media] si2157: change command for sleep

[media] si2157: change command for sleep

Instead of sending command 13 to the tuner, send command 16 when sleeping. This
behaviour is observed when using manufacturer provided binary-only Linux driver
for TechnoTrend CT2-4400 (Windows driver does not do power management).

The issue with command 13 is that firmware loading is necessary after that.
This is not an issue with tuners that do not require firmware, but starting
streaming after sleep on an Si2158 takes noticeable time as firmware is
loaded on resume.

Signed-off-by: Olli Salonen <olli.salonen@iki.fi>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>