arm64: allwinner: a64: add UART1 pin nodes

On many boards UART1 connects to a Bluetooth chip, so add the pinctrl
nodes for the only pins providing access to that UART. That includes
those pins for hardware flow control (RTS/CTS).

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