[audio-core] clang-tidy fixes in audio_dfx.so

This CL addresses the clang-analyzer-security, clang-analyzer-core,
clang-analyzer-optin.cplusplus and clang-analyzer-deadcode warnings
generated by git-file-tidy --all.

Test: build, CQ, "git-file-tidy --all" is clean

Change-Id: Ie4f639d65c1e716c131ea3aae4ed10df819e8609
2 files changed