V4L/DVB (3292): Fix signed/unsigned bug in brightness handling of cx25840

- Fix signed/unsigned bug in brightness handling (set to 0 and 128 was returned).

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@brturbo.com.br>
diff --git a/drivers/media/video/cx25840/cx25840-core.c b/drivers/media/video/cx25840/cx25840-core.c
index b93495b..29b378b 100644
--- a/drivers/media/video/cx25840/cx25840-core.c
+++ b/drivers/media/video/cx25840/cx25840-core.c
@@ -457,7 +457,7 @@
 		ctrl->value = state->pvr150_workaround;
 		break;
 	case V4L2_CID_BRIGHTNESS:
-		ctrl->value = cx25840_read(client, 0x414) + 128;
+		ctrl->value = (s8)cx25840_read(client, 0x414) + 128;
 		break;
 	case V4L2_CID_CONTRAST:
 		ctrl->value = cx25840_read(client, 0x415) >> 1;