V4L/DVB (9764): em28xx: Add support for suspend the device when not used

Several chips may be turned off when the device is not used, like audio,
video and dvb demods. This patch adds a gpio callback at the core
structs to allow turning off such devices.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/em28xx/em28xx-cards.c b/drivers/media/video/em28xx/em28xx-cards.c
index be78485..a4b61e5 100644
--- a/drivers/media/video/em28xx/em28xx-cards.c
+++ b/drivers/media/video/em28xx/em28xx-cards.c
@@ -1456,7 +1456,7 @@
 	em28xx_set_mode(dev, EM28XX_ANALOG_MODE);
 
 	/* Unlock device */
-	em28xx_set_mode(dev, EM28XX_MODE_UNDEFINED);
+	em28xx_set_mode(dev, EM28XX_SUSPEND);
 }
 
 static void em28xx_setup_xc3028(struct em28xx *dev, struct xc2028_ctrl *ctl)