thermal: sun8i: add TEMP_CALIB_MASK for calibration data in sun50i_h6_ths_calibrate

For sun50i_h6_ths_calibrate(), the data read from nvmem needs a round of
calculation. On the other hand, the newer SOC may store other data in
the space other than 12bit sensor data. Add mask operation to read data
to avoid conversion error.

Signed-off-by: Yangtao Li <frank@allwinnertech.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/dcf98648c16aff7649ff82438bfce6caae3e176f.1595572867.git.frank@allwinnertech.com