[MLAS] Fix SVE enabled pipeline break (#26203)
### Description
The `MLAS_USE_SVE` macro was missing for some unittests/benchmark
targets. In the original PR, it was scoped down to just the mlas target
and this resulted in different mlas platform struct definitions across
targets.
### Motivation and Context
Fix pipeline crash and unblock daily pipeline run
#25238 (change that introduced the issue)
