thermal: exynos: Document compatible for Exynos5433 TMU

Commit 488c7455 ("thermal: exynos: Add the support for Exynos5433
TMU") added new compatible but forgot to update documentation.

Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>