Fix handling of custom configuration with 8 motors, enabling motor testing on octocopters

[Patronics]

Resolves issue #4212

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[nerdCopter]

@limonspb , please check. although it obviously works, i feel it might should be part of the loop or may need to be set with some if/then statement.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[limonspb]

@limonspb , please check. although it obviously works, i feel it might should be part of the loop or may need to be set with some if/then statement.

@Patronics did you check if it works ok and/or for standard mixers, and also for motor remapping and motor order dialogs, please?

[haslinghuis]

@limonspb already tested - this just fixes the assumption made in #2436

See #4213 (comment)

[Patronics]

@limonspb , please check. although it obviously works, i feel it might should be part of the loop or may need to be set with some if/then statement.

@Patronics did you check if it works ok and/or for standard mixers, and also for motor remapping and motor order dialogs, please?

I've tested the standard mixers, they all seem to behave properly, with one exception, which seems to not quite behave properly before this change either, so seems to be an unrelated bug?

When I tried setting the "Singlecopter" mixer, after a reboot it always seems to be set to the custom mixer instead of singlecopter, and from there it seems to persist whatever motor configuration was added in custom, rather than using the singlecopter mixer? But again the same broken behavior is observed with the released version of betaflight configurator 10.10.0, so I don't believe the issue is related to this PR. It seems to have been documented in the issue betaflight/betaflight#10641, so already a known behavior.

[haslinghuis]

@Patronics see betaflight/betaflight#10641 (comment) why that happens.