mesa: don't leak interface_name

Found by Coverity

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Timothy Arceri <t_arceri@yahoo.com.au>

src/mesa/main/shader_query.cpp

@@ -995,6 +995,7 @@ program_resource_top_level_array_stride(struct gl_shader_program *shProg,
       }
    }
 found_top_level_array_size:
+   free(interface_name);
    free(var_name);
    return array_stride;
 }