[media] v4l: omap3isp: Fix sub-device power management code

Commit 813f5c0a ("media: Change media device link_notify behaviour")
modified the media controller link setup notification API and updated the
OMAP3 ISP driver accordingly. As a side effect it introduced a bug by
turning power on after setting the link instead of before. This results in
sub-devices not being powered down in some cases when they should be. Fix
it.

Fixes: 813f5c0a

 [media] media: Change media device link_notify behaviour

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Cc: stable@vger.kernel.org # since v3.10
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>