oniro-openharmony-linux: allow running the system without hdmi connected
enable HDMI_FORCE_HOTPLUG to allow running the system without an hdmi display connected. HDMI_FORCE_HOTPLUG configuration does not work with vc4-kms-v3d dtoverlay, therefore using vc4-fkms-v3d instead.
Signed-off-by: Francesco Pham francesco.pham@huawei.com