This new function uses igt_edid to generate an EDID suitable for testing HDMI
audio. It's imported from kms_chamelium with minor edits, it's used there and
in kms_hdmi_inject. A (unexported for now) generate_hdmi_audio_edid function
enables generation of EDIDs with arbitrary SAD and speaker blocks.

This obsoletes kmstest_edid_add_audio.

The sanity check for the HDMI audio EDID has been moved from
lib/tests/igt_hdmi_inject.c to lib/tests/igt_edid.c.

Signed-off-by: Simon Ser <simon.ser@intel.com>
Reviewed-by: Martin Peres <martin.peres@linux.intel.com>