arm64: dts: apq8096-db820c: Add HDMI display support

The APQ8096 DB820c platform provides HDMI output. The MDSS block on
8x96 supports a direct HDMI out. Populate the MDSS, MDP and HDMI DT
nodes. Also, add the HDMI HPD and DDC pinctrl nodes with the bias
and driver strength specified for this platform.

Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Andy Gross <agross@kernel.org>