arm64: defconfig: Enable video capture drivers on imx8mm/imx8mn

The imx8m Mini and imx8m Nano both use the same CSIS driver for
interfacing with sensors and cameras.  The Mini routes the CSIS
output to the imx7-CSI driver, and the Nano routes the CSIS
through the imx8-isi driver like the one used on the imx8mp.

Enable the drivers necessary to facilitate capture on both of
these two platforms.

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>