Fix two kernel doc warnings introduced by the recent DP audio patch:

- Add a doc line for the new "audio" field
- Remove a reference to zynqmp_dpsub.c from zynqmp.rst, as the .c file
  no longer has structured comments

Fixes: 3ec5c1579305 ("drm: xlnx: zynqmp_dpsub: Add DP audio support")
Closes: https://lore.kernel.org/all/20241220154208.720d990b@canb.auug.org.au/
Reviewed-by: Vishal Sagar <vishal.sagar@amd.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241220-xilinx-dp-audio-doc-fix-v1-1-cc488996e463@ideasonboard.com
(cherry picked from commit 96b5d2e807f667320c66f41ddc1c473023a73ab2)
Signed-off-by: Maxime Ripard <mripard@kernel.org>

Add a debugfs interface for exercising the various test modes supported
by the DisplayPort controller. This allows performing compliance
testing, or performing signal integrity measurements on a failing link.
At the moment, we do not support sink-driven link quality testing,
although such support would be fairly easy to add.

Additionally, add some debugfs files for ignoring AUX errors and HPD
events, as this can allow testing with equipment that cannot emulate a
DPRX.

Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
[Tomi: fixed a few minor formatting issues]
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240809193600.3360015-9-sean.anderson@linux.dev