thermal/drivers/thermal_helpers: Sort headers alphabetically

Sort headers to make it easier to read and find duplicate headers.

Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/133db154796f354e6c51e6310095f679e1f45441.1589199124.git.amit.kucheria@linaro.org