Fix for esp32c6

[ptxmac]

Description

A minor fix so esp-idf-cxx can compile correctly for esp32c6 (and maybe other?)

i2c_cxx incorrectly assumed that I2C_NUM_1 would exist if SOC_I2C_NUM >= 2. But that's not the case when the device has 1 HP i2c and 1 LP i2c.

This changes i2c_cxx to look at only the HP SOC_HP_I2C_NUM instead

Testing

My own code compiles now 😄

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Checklist

Before submitting a Pull Request, please ensure the following:

• 🚨 This PR does not introduce breaking changes.
• All CI checks (GH Actions) pass.
• Documentation is updated as needed.
• Tests are updated or added as necessary.
• Code is well-commented, especially in complex areas.
• Git history is clean — commits are squashed to the minimum necessary.

[CLAassistant]

All committers have signed the CLA.

[ptxmac]

Tests fails for unrelated reasons