icepick: use formatting macros for debugging

[xobs]

Detailed description

Use PRIu32 for formatting the uint32_t icepick_idcode value. This is required when building for targets where %u doesn't mean uint32_t.

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• I've read the Code of Conduct
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• It builds for hardware native (see Building the firmware)
• It builds as BMDA (see Building the BMDA)
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[dragonmux]

Ah, yes - our bad! Thanks for noticing and fixing this, LGTM - so merging. Thank you for the contribution!