[non-be][rend-non-be][split-non-be]Fix eig2x2_fx optimisation

• Related issues: #2292 (closed), also solves #2266 (closed)
• Requested reviewers: @malenovskyvl

Reason why this change is needed

The eig2x2_fx optimisation (#NONBE_OPT_2193_EIG2X2) is triggering an assert (frame 3010) in one long test vector test (test_param_file_tests[ltv-SBA 3OA bitrate switching from 13.2 kbps to 512 kbps, 48kHz in, 48kHz out, BINAURAL out (Model from file)])

Description of the change

Bug in direction of scaling has been fixed