dt-bindings: hwmon: Convert lm75 bindings to yaml

In order to automate the verification of DT nodes convert lm75.txt to
lm75.yaml.

Signed-off-by: Alban Bedel <alban.bedel@aerq.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201001145738.17326-2-alban.bedel@aerq.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>