Make dmg-audio tests pass

Should fix blargg audio tests pass.

Related to #18

The strategy here involved:

• Implementing the global audio registers
• Implementing all the read register operations
• Going step by step over the multiple tests
• Reading the source of the tests to control fixing
• Used the 'dmg_sound/rom_singles' files for test by test execution

.github/workflows/main.yml

@@ -118,7 +118,7 @@ jobs:
       - name: Verify Rust code format
         run: cd frontends/sdl && cargo fmt --all -- --check
       - name: Verify Rust code linting
-        run: cd frontends/sdl && cargo clippy -- -D warnings -A unknown-lints
+        run: cd frontends/sdl && cargo update -p half --precise 2.2.1 && cargo clippy -- -D warnings -A unknown-lints
       - name: Run unit tests
         run: cd frontends/sdl && cargo test
       - name: Build development version