Use the i2c-mux.yaml schema in the maxim,max9286 binding schema. With this,
several properties can be dropped as they are defined in i2c-mux.yaml
already.

Cc: Jacopo Mondi <jacopo+renesas@jmondi.org>
Cc: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Cc: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Wolfram Sang <wsa@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210526184839.2937899-7-robh@kernel.org