dt-bindings: atmel-usart: Add microchip,sam9x60-{usart, dbgu}

Add microchip,sam9x60-usart and add microchip,sam9x60-dbgu to DT
bindings documentation.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
1 file changed