Security
   * Limit the size of calculations performed by mbedtls_mpi_exp_mod to 
     MBEDTLS_MPI_MAX_SIZE to prevent a potential denial of service when 
     generating Diffie-Hellman key pairs. Credit to OSS-Fuzz.
Security
   * Limit the size of calculations performed by mbedtls_mpi_exp_mod to
     MBEDTLS_MPI_MAX_SIZE to prevent a potential denial of service when
     generating Diffie-Hellman key pairs. Credit to OSS-Fuzz.

Fix whitespace in changelog entry
Fix whitespace in changelog entry

Extra whitespace and a missing newline at end of file was causing an error with
`check_files.py`.

Signed-off-by: Chris Jones <cbf609b812bf58762ceb89e8692559dbbe9149ea@arm.com>
