pico-imx6ul: Update the defconfig

The defconfig/config.h file were merged but were already out of sync
with mainline.  This brings them further into line now.

Cc: Richard Hu <richard.hu@technexion.com>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Tom Rini <trini@konsulko.com>