Resolve "Warnings with gcc 12.2.0 (Debian 12)"

• Related issues: #938 (closed)
• Requested reviewers: @fotopoulou

Reason why this change is needed

• Fix compiler warning in ivas_mdct_core_reconstruct()

Description of the change

• Describe what is done.

Affected operating points

• Everything is BE

Related to #938 (closed)