arm64: dts: ti: am625-sk: Add overlay for HDMI audio

Enable audio output over HDMI instead of the 3.5mm jack.

A FET switch (U65) on the EVM muxes serial audio lines coming from McASP
between the codec (tlv320aic3106) and the HDMI bridge (sii9022).

By default it uses the codec, but it can be toggled to use the HDMI
bridge by shorting a (J24) header on the board.

Signed-off-by: Jai Luthra <j-luthra@ti.com>
Tested-by: Aradhya Bhatia <a-bhatia1@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>