V4L/DVB (8123): Add support for em2860 based PointNix Intra-Oral Camera

em28xx-cards.c
em28xx-input.c
em28xx-video.c
em28xx.h
 - Add support for the PointNix Intra-Oral Camera, which required addition of
   a construct for reading the "snapshot" button (provided on the em2860 and
   em2880 chips, but this is the first case where I have seen it actually used
   in a product). The button is wired to pin 56 on the em2880.

   http://www.pointnix.com/ENG/dental/product_02.asp

   Thanks to Roberto Mantovani <rmantovani@libero.it> for testing the changes

Signed-off-by: Devin Heitmueller <devin.heitmueller@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
diff --git a/drivers/media/video/em28xx/em28xx-video.c b/drivers/media/video/em28xx/em28xx-video.c
index 1c3e8b6..2d9f14d 100644
--- a/drivers/media/video/em28xx/em28xx-video.c
+++ b/drivers/media/video/em28xx/em28xx-video.c
@@ -1590,6 +1590,8 @@
 				dev->vdev->minor-MINOR_VFL_TYPE_GRABBER_MIN,
 				dev->vbi_dev->minor-MINOR_VFL_TYPE_VBI_MIN);
 	list_del(&dev->devlist);
+	if (dev->sbutton_input_dev)
+		em28xx_deregister_snapshot_button(dev);
 	if (dev->radio_dev) {
 		if (-1 != dev->radio_dev->minor)
 			video_unregister_device(dev->radio_dev);