Add support for audioinjector.net ultra soundcard. (#2664)

Uses the simple-audio-card ALSA machine driver. Sets up the machine
driver in the device tree overlay file. The overlays/Makefile is
altered to add the audioinjector-ultra.dtbo dtb overlay.

Adds CONFIG_SND_SOC_CS4265 to the defconfig files.

Signed-off-by: Matt Flax <flatmax@flatmax.org>