ARM: dts: sunxi: Fix CPU thermal zone node name

The CPU thermal zone is called on most of the older DTSI cpu_thermal.
However, the underscore is an invalid character for a node name and the
thermal zone binding explicitly requires that zones are called
*-thermal. Let's fix it.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Jernej Skrabec <jernej.skrabec@siol.net>
Link: https://lore.kernel.org/r/20210114113538.1233933-8-maxime@cerno.tech