drm/i915/audio: fix indentation, remove extra braces

Cleanup the code. No functional changes.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/6c2f6afa4c8866f8c1714b4f8dba9ea2d1509e4a.1620115983.git.jani.nikula@intel.com