ARM: dts: keystone-k2g-evm: add HDMI video support

Add DT nodes for HDMI video support for K2G EVM. The HDMI uses SiI9022
DPI as HDMI encoder. The DSS DPI is connected to SiI9022 HDMI
encoder's video input and encoder's output goes to HDMI connector.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>