mesa/glformats: make _mesa_gles_error_check_format_and_type() more consistent

Let's consistently use the following code format instead of relying on
falling through to `default`:

    if (!req)
       return GL_INVALID_OPERATION;
    break;

Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5729>
1 file changed