Fix clock on Heltec T1: Do not misidentify IMU as an RTC

[beala]

The T1 has an ICM-42607-P IMU with the same address as a DS3231 RTC. This completely breaks the clock on the T1. Reading the time results in a garbage value, causing all sorts of strange issues. I noticed this because the time never advances, which breaks logging in to repeaters (due to their time-based replay protection).

This simply disables the probe on the I2C line. The DS3231 doesn't have a WHO_AM_I register that could be used to prevent misidentifying it, so this simpler fix is used.

Here is the schematic showing the IMU: https://resource.heltec.cn/download/Mesh_Node_T1/schematic/Mesh_Node_T1_V1.0.pdf

Pin 1 is tied to GND, which sets the address to 1101000 or 0x68 (datasheet), same as the DS3231.

MeshCore/src/helpers/AutoDiscoverRTCClock.cpp

Line 18 in 0679dbe

#define DS3231_ADDRESS 0x68

Testing

Without this fix, the time doesn't update:

alex@thinkpad ~/w/MeshCore> meshcore-cli -S
40C140D1|* clock
Current time : 1999-12-31 18:09:00 (946688940)
40C140D1|* clock sync
Time synced
40C140D1|* clock
Current time : 1999-12-31 18:09:00 (946688940)

With this fix:

40C140D1|* clock
Current time : 2024-05-15 05:22:46 (1715772166)
40C140D1|* clock sync
Time synced
40C140D1|* clock
Current time : 2026-08-25 15:29:19 (1787693359)

Here's the ble companion firmware if anyone wants to try flashing it at https://meshcore.io and testing it.
firmware.zip

[beala]

cc @Quency-D who PR'd initial support for this #2520