ARM: dts: sun8i: a83t: Add I2S controller device nodes

The A83T has 3 I2S controllers. The first is multiplexed with the TDM
controller. The pins are generally connected to the codec side of the
AXP81x PMIC/codec/RTC chip. The second is free for other uses. The
third only supports output, and is connected internally to the HDMI
controller for HDMI audio output.

This patch adds device nodes for the controllers, and a default pinmux
setting for the second controller.

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