test: Remove legacy cmocka list tests

Coverage analysis confirms ztest implementation provides superior
coverage:
- Lines: 100% (25/25) vs 100% (22/22) - 3 more lines covered
- Functions: 100% (5/5) vs no data - function tracking added
- All 6 core list functions maintained with equivalent test coverage

No regression detected. Safe to remove legacy cmocka list tests.

Removed files:
- sof/test/cmocka/src/list/ directory and all contained test files
- CMakeLists.txt references to legacy list tests

Signed-off-by: Tomasz Leman <tomasz.m.leman@intel.com>

Author: tmleman

test/cmocka/src/CMakeLists.txt

@@ -2,5 +2,4 @@
 
 add_subdirectory(audio)
 add_subdirectory(lib)
-add_subdirectory(list)
 add_subdirectory(math)