openharmony-linux: disable not used DISTRO_FEATURES

In order to control what we ship and being responsible for, as well as
reducing the image size, we start with disabling DISTRO_FEATURES we
inherited from Poky. These are simply default values Poky uses to show
what Yocto/OE can do. They have currently no use for us and we can still
bring them back when the use cases arises.

Before:
build tasks: 5795 (26m)
du -cs tmp/deploy/images/stm32mp1-av96/openharmony-image-extra-stm32mp1-av96-20210301211000.rootfs.tar.xz
46624

After:
build tasks: 5159 (24m)
du -cs tmp/deploy/images/stm32mp1-av96/openharmony-image-extra-stm32mp1-av96-20210301215709.rootfs.tar.xz
43420

Signed-off-by: Stefan Schmidt <stefan.schmidt@huawei.com>