arm64: dts: qcom: qcm6490-fairphone-fp5: Enable USB audio offload support

arm64: dts: qcom: qcm6490-fairphone-fp5: Enable USB audio offload support

Enable USB audio offloading which allows to play audio via a USB-C
headset with lower power consumption and enabling some other features.

This can be used like the following:

  $ amixer -c0 cset name='USB_RX Audio Mixer MultiMedia1' On
  $ aplay --device=plughw:0,0 test.wav

Compared to regular playback to the USB sound card no xhci-hcd
interrupts appear during playback, instead the ADSP will be handling the
USB transfers.

Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250801-fp5-usb-audio-offload-v1-2-240fc213d3d3@fairphone.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>