Merge pull request #8940 from paul-elliott-arm/add_fixes_to_threading_changelog

Add issues fixed to threading MVP changelog entry

Author: paul-elliott-arm

ChangeLog.d/add_threading_changelog.txt

@@ -4,3 +4,4 @@ Features
      concurrently calling psa_crypto_init() when MBEDTLS_THREADING_C and
      MBEDTLS_THREADING_PTHREAD are defined. See
      docs/architecture/psa-thread-safety/psa-thread-safety.md for more details.
+     Resolves issues #3263 and #7945.