dt-bindings: thermal: sun8i: Fix misplaced schema keyword in compatible strings

A compatible string 'enum' mistakenly has 'const: ' in the compatible
strings. Remove these.

Fixes: 0b28594d ("dt-bindings: thermal: Add YAML schema for sun8i-thermal driver bindings")
Cc: Vasily Khoruzhick <anarsoul@gmail.com>
Cc: Yangtao Li <tiny.windzz@gmail.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Amit Kucheria <amitk@kernel.org>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Jernej Skrabec <jernej.skrabec@siol.net>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20210202181538.3936235-1-robh@kernel.org