Temperature reading underflows on 32-bit micros

[jim-sokoloff]

• Arduino board: ESP32 WROOM-32

• Arduino IDE version (found in Arduino -> About Arduino menu): 1.8.12

• List the steps to reproduce the problem below (if possible attach a sketch or copy the sketch code in too):

  1. Use the library example code adafruit_lsm6ds33_test.ino on any 32-bit micro.
  2. Cool the temp sensor below 25.0ºC
  3. Observe that the temp sensor reports 280.9ºC instead of 24.9ºC (off by 256.0 for all values under 25.0).

Fix submitted in PR#16.