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: NHans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: NMauro Carvalho Chehab <mchehab@brturbo.com.br>

drivers/media/video/cx25840/cx25840-core.c

@@ -457,7 +457,7 @@ static int get_v4lctrl(struct i2c_client *client, struct v4l2_control *ctrl)
 		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;