arm: dts: sun8i: a83t: Add the UART1 controller

The A83T has an UART1 controller, with the RTS and CTS pins routed so it
can be used for devices with hardware flow control, like a bluetooth chip.

Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>