ASoC: dt-bindings: mt8192-mt6359: Fix indentation

The items of the 'maintainers' list are indented with three spaces.
Use the usual two spaces instead, for consistency and to silence
yamllint.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Link: https://lore.kernel.org/r/20210116013403.3490518-1-j.neuschaefer@gmx.net
Signed-off-by: Mark Brown <broonie@kernel.org>