Resolve "CMake build fails with -DINCLUDE_SPLIT=1" on Linux

• Related issues: #823 (closed)
• Requested reviewers: @sagnowski @haeussler

Reason why this change is needed

• CMake build on Linux fails to build ivas_lc3plus_unit_test

Description of the change

• CMakeLists.txt was updated to reflect the file structure in the lib_rend directory
• Missing preprocessor switches (SPLIT_REND_WITH_HEAD_ROT) were added to LC3plus split rendering files

Affected operating points

• CMake build framework

Related to #823 (closed)