media: imx-csi: fix burst size

Setting a burst size of "8" doesn't work for IMX219 with 8-bit bayer,
but a burst size of "16" does.  Fix this.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>