ARM: imx_v6_v7_defconfig: Enable AC97 codec support

imx6qdl udoo board has an AC97 codec.

Add support for it by default.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Acked-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>