Fix wrong test for BOXMSPOVERRIDE channel

[ledvinap]

msp_override_channels_mask bits are indexed by raw channels, but auxChannelIndex (starting from NON_AUX_CHANNEL_COUNT) was used for test

[github-actions]

Do you want to test this code? You can flash it directly from Betaflight Configurator:

• Simply put #12857 (this pull request number) in the Select commit field of the Configurator firmware flasher tab (you need to Enable expert mode, Show release candidates and Development).

WARNING: It may be unstable. Use only for testing!

[ledvinap]

@cvetaevvitaliy : Can you please test it?

[blckmn]

AUTOMERGE: (FAIL)

• github identifies PR as mergeable -> FAIL
• assigned to a milestone -> PASS
• cooling off period lapsed -> PASS
• commit count less or equal to three -> PASS
• Don't merge label NOT found -> PASS
• at least one RN: label found -> PASS
• Tested label found -> FAIL
• assigned to an approver -> PASS
• approver count at least three -> FAIL

[cvetaevvitaliy]

@cvetaevvitaliy : Can you please test it?

Hi!
Yes, I can test this fix tomorrow

[Automate5462]

I tried to achieve the same, but it does not work:
When msp_override_channels_mask is set to zero in betaflight cli, then the msp override mode disappears.
And when it is set to e.g. =1, then the msp override mode can be set, and assigned to e.g. AUX2.
But once the AUX2 triggers this mode, it is not possible to exit from this mode, as the AUX channels are not responding anymore to the transmitter.
Does anybody know, what needs to be done, so that the AUX-channels are not overwritten by the msp, but always taken from the transmitter?
(So that the transmitter can always start and stop the mode, when the msp overwrites the pitch, roll, yaw and throttle?)