Document TFA9897 bindings.
Signed-off-by: Vincent Knecht <vincent.knecht@mailoo.org>
Reviewed-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20210528105101.508254-1-vincent.knecht@mailoo.orgSigned-off-by: Mark Brown <broonie@kernel.org>