dt-bindings: mfd: Convert tps65086.txt to YAML

This converts the tps65086.txt binding description to YAML schema so
dts files can be verified automatically.

Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>