ARM: dts: sun8i: enable UART1 for iNet D978 Rev2 board

UART1 is connected to the bluetooth part of RTL8723BS WiFi/BT combo card
on iNet D978 Rev2 board.

Enable the UART1 to make it possible to use the modified hciattach by
Realtek to drive the BT part of RTL8723BS.

On the board no r_uart pins are found now (the onboard RX/TX pins are
wired to PF2/PF4, which is muxed with mmc0), so also disabled it.

Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>