Add board definitions for GS1920-8HPv2, GS1920-24v2, GS1920-24HPv2, GS1920-48v2 and GS1920-48HPv2 to allow building accepted upgrade images. Link: https://github.com/openwrt/firmware-utils/pull/69 Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>