fix: able to set limits and setpoint to zero

[hoegge]

With the current implementation you cannot set any of the limits or the setpoint to zero, since 0 is falsy.

• Bugfix (non-breaking change which fixes an issue)
• [] New feature (non-breaking change which adds functionality)

Proposed changes

You cannot set, e.g., low limit to 0 since 0 is falsy. Checking limits and setpoint for zero now and sets to 0 instead of default values in that case, which will confuse people.

Checklist

• I have read the contribution guidelines

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: hoegge / name: Morten H Pedersen (eeb8a96)

[dceejay]

Good catch . Thanks !