MAINTAINERS: add include/dt-bindings/thermal to THERMAL

Maintainers of the directory Documentation/devicetree/bindings/thermal
are also the maintainers of the corresponding directory
include/dt-bindings/thermal.

Add the file entry for include/dt-bindings/thermal to the appropriate
section in MAINTAINERS.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20220613124309.28790-1-lukas.bulwahn@gmail.com


Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>