Add DT compatible string for DHCOR Testbench board, which is a testbench for testing of DHCOR SoM during manufacturing. This is effectively a trimmed down version of AV96 board with CSI-2 bridge, HDMI bridge, WiFi, Audio and LEDs removed and used as GPIOs instead. Signed-off-by: Marek Vasut <marex@denx.de> Acked-by: Rob Herring <robh@kernel.org> Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>