ARM: dts: sun8i: Add CPUCFG device node for A83T dtsi

As we found in sun9i-a80, CPUCFG is a collection of registers that are
mapped to the SoC's signals from each individual processor core and
associated peripherals.

These registers are used for SMP bringup and CPU hotplugging.

Signed-off-by: Mylène Josserand <mylene.josserand@bootlin.com>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>