doc: DT: Add ti,da830-uart to serial/8250 bindings

This adds the ti,da830-uart compatible string to serial 8250 UART bindings.

Signed-off-by: David Lechner <david@lechnology.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>