thermal: Fix couple of spellos in the file sun8i_thermal.c

s/calibartion/calibration/
s/undocummented/undocumented/

Signed-off-by: Bhaskar Chowdhury <unixbhaskar@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210305014348.17412-1-unixbhaskar@gmail.com