ASoC: meson: axg-tdm-formatter: add reset to the bindings documentation

Add an optional reset property to the tdm formatter bindings. The
dedicated reset line is present on some SoC families, such as the g12a.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://lore.kernel.org/r/20190703120749.32341-2-jbrunet@baylibre.com


Signed-off-by: Mark Brown <broonie@kernel.org>