V4L/DVB (12405): em28xx-cards: move register 0x13 setting to the proper place

Register 0x13 seems to be a sort of image control, maybe gamma, white
level or black level. Lower values produce better images, while higher
values increases the contrast and shifts colors to green. 0xff produces
a black image. This register is not Silvercrest-specific, so its code
should be moved to a better place.

If this register is left alone, a random value can be found at the
register, producing weird results.

While here, let's remove register 0x0d, as it had no noticed effect at
the image.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/em28xx/em28xx-cards.c

@@ -2273,10 +2273,6 @@ void em28xx_card_setup(struct em28xx *dev)
 		em28xx_gpio_set(dev, dev->board.tuner_gpio);
 		em28xx_set_mode(dev, EM28XX_ANALOG_MODE);
 		break;
-	case EM2820_BOARD_SILVERCREST_WEBCAM:
-		/* FIXME: need to document the registers bellow */
-		em28xx_write_reg(dev, 0x0d, 0x42);
-		em28xx_write_reg(dev, 0x13, 0x08);
 	}
 
 	if (dev->board.has_snapshot_button)

drivers/media/video/em28xx/em28xx-core.c

@@ -632,6 +632,9 @@ int em28xx_capture_start(struct em28xx *dev, int start)
 		return rc;
 	}
 
+	if (dev->board.is_webcam)
+		rc = em28xx_write_reg(dev, 0x13, 0x0c);
+
 	/* enable video capture */
 	rc = em28xx_write_reg(dev, 0x48, 0x00);