Fix/aanderaa errata 2.2.26

[matt001k]

What changed?

This addresses STM32U5 errata 2.2.26 in the lptimtick_u5.c module which states:

The device hangs up when it enters low-power modes (Stop 0, 1, 2, 3 / Standby / Shutdown) if the following
conditions are met:
• An asynchronous wake-up event or interrupt occurs within a short timing window (six HCLK‑cycles‑lengths)
before entering low‑power mode.
• A low-power mode code entry is executed from flash memory (ICACHE enabled or not).
• Flash prefetch is enabled.
• Flash latency is equal to or greater than four wait‑states.

How does it make Bristlemouth better?

The Aanderaa application was resetting at random intervals (2-45 minutes).
This fix addresses the reason why!

Where should reviewers focus?

The following link is to the errata.

Checklist

• Add or update unit tests for changed code
• Ensure all submodules up to date. If this PR relies on changes in submodules, merge those PRs first, then point this PR at/after the merge commit
• Ensure code is formatted correctly with clang-format. If there are large formatting changes, they should happen in a separate whitespace-only commit on this PR after all approvals.