[mitigation] CLANG commandline option `mcpu=cortex-m55 -mfpu=fpv5-sp-d16` can lead to fatal error in backend

[jkrech]

Describe the mitigation for the bug
Bug: arm/arm-toolchain#861
Summary: When selecting Compiler:CLANG and a device with processor Cortex-M55 with FPU:enabled this may lead to fatal error during compilation.

To Reproduce
See: arm/arm-toolchain#861

Expected behavior
All modules compile successfully

Environment (please complete the following information):

• LLVM Embedded Toolchain
• Version 22.1.0
• OS: any

Additional context
Recommendation is to not select FPU independently.
If we select FPU it needs to be:

-mfpu=fp-armv8-fullfp16-d16