Support for HPE 1920 images depends on two non-existent tools (mkh3cimg
and mkh3cvfs) from the in the firmware-utils package. Revert commit
f2f09bc002 ("realtek: add support for HPE 1920 series") until support
for these tools is merged and made available in OpenWrt.
Signed-off-by: Sander Vanheule <sander@svanheule.net>