ARM: imx_v6_v7_defconfig: add imx7ulp support

Select CONFIG_SOC_IMX7ULP by default.
Patch generated via make ARCH=arm savedefconfig

Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <kernel@pengutronix.de>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>