dt-bindings: thermal: tsens: support per-sensor calibration cells

Allow specifying the exact calibration mode and calibration data as nvmem
cells, rather than specifying just a single calibration data blob.

Note, unlike the vendor kernel the calibration data uses hw_ids rather
than software sensor indices (to match actual tsens usage in
thermal zones).

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>