Fix all doxygen warnings

Change-Id: Ic312bc3771a69765b43f1a7c025f1f57783823c0
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/49741
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>

src/reader/spirv/entry_point_info.h

@@ -29,6 +29,10 @@ struct EntryPointInfo {
   /// Constructor.
   /// @param the_name the name of the entry point
   /// @param the_stage the pipeline stage
+  /// @param the_owns_inner_implementation if true, this entry point is
+  /// responsible for generating the inner implementation function.
+  /// @param the_inner_name the name of the inner implementation function of the
+  /// entry point
   /// @param the_inputs list of IDs for Input variables used by the shader
   /// @param the_outputs list of IDs for Output variables used by the shader
   EntryPointInfo(std::string the_name,

src/reader/spirv/parser_impl.h

@@ -68,6 +68,7 @@ struct TypedExpression {
   TypedExpression(const TypedExpression&);
 
   /// Assignment operator
+  /// @returns this TypedExpression
   TypedExpression& operator=(const TypedExpression&);
 
   /// Constructor