11 scrutinizer-related issues to fix

[ronanguilloux]

see https://scrutinizer-ci.com/g/ronanguilloux/php-gpio/inspections/a97307d9-9d52-486f-9cae-1f31e7e1b833/issues/?status=all

& this :

The return type of return false; (false) is incompatible with the return type declared by the interface PhpGpio\Sensors\SensorInterface::write of type PhpGpio\Sensors\SensorInterface.

see https://scrutinizer-ci.com/g/ronanguilloux/php-gpio/inspections/1115dd77-1c88-4880-88e4-d8d4c583ce78/issues/files/src/PhpGpio/Sensors/MCP3002.php?status=new&orderField=path&order=asc&issueId=00feb1ee-9b1e-42e1-8b36-e5c97bb9fd39