imx8mm: configs: enable distro default features

imx8mm ekv has been switched to use distro boot commands, but had no
correct options enabled to support sysboot.
According to the README.distro, sysboot is consindered to be a
recommended way of using distro boot commands, it required default distro
features to be enabled instead of only those that are relevant to the boot
script.

Replace the boot script specific options in the config to a default distro
option.

Signed-off-by: Andrey Zhizhikin <andrey.zhizhikin@leica-geosystems.com>
Cc: Peng Fan <peng.fan@nxp.com>
Fixes: 2df8930b ("imx8mm: configs: add support for distro boot commands")
Reviewed-by: Fabio Estevam <festevam@gmail.com>