[media] gspca - sonixj: Fix wrong register mask for sensor om6802

The bug was introduced by git commit 0e4d413a, giving very dark images.
Signed-off-by: Luiz Carlos Ramos <lramos.prof@yahoo.com.br>
Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/gspca/sonixj.c

@@ -2386,7 +2386,7 @@ static int sd_start(struct gspca_dev *gspca_dev)
 		reg_w1(gspca_dev, 0x01, 0x22);
 		msleep(100);
 		reg01 = SCL_SEL_OD | S_PDN_INV;
-		reg17 &= MCK_SIZE_MASK;
+		reg17 &= ~MCK_SIZE_MASK;
 		reg17 |= 0x04;		/* clock / 4 */
 		break;
 	}