Matek H743 servos issue on boot sometimes. Fix exists but needs to be added to ardupilot.

## Bug report

**Issue details**

Servos go to full deflection on boot some times and it damages hardware. @andyp1per has already created a fix that I have tested some and it appears to solve the issue. The code just needs to be merged I think so Matek H743 users can go to new versions of ardupilot.

**Version**
4.3.7 through 4.5.7 at least. I assume all previous versions

**Platform**
[x] All
[ ] AntennaTracker
[ ] Copter
[ ] Plane
[ ] Rover
[ ] Submarine

**Airframe type**
I discovered this on a Traditional Helicopter.

**Hardware type**
Matek H743 Mini

**Logs**

Previous discussion: https://discuss.ardupilot.org/t/servos-some-times-go-crazy-on-start-up/98641/56
Fix already created by @andyp1per that I have tested some already. Seems to fix the issue.

Please add @andyp1per's code to regular ardupilot code so I can use new versions of ardupilot. It looks like just a few lines so I hope this is a pretty simple fix.

Start with the linked forum discussion and the fix attributed to @andyp1per; locate the corresponding ArduPilot startup and servo code for the Matek H743 Mini. Reproduce or review the boot-time full-deflection behavior, then verify that the proposed change prevents unsafe servo movement on boot.

Written by the indexing model from the issue text.