ARM: dts: sun8i-a83t: Correct low speed oscillator clocks

The A83T does not have a 32.768 kHz low speed oscillator, either as
an external crystal or input. It has a 16 MHz RC-based (inaccurate)
internal oscillator, which is then divided by 512 for a clock close
to 32 kHz.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Vishnu Patekar <vishnupatekar0510@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>