sensor: tmp116: Add support for tmp117, fix calculation issues

- Added support for TMP117 in existing driver for TMP116
  The Texas Instruments TMP117 is a higher precision upgrade
   from TMP116. It shares most functionality, but has a
   differing device ID.
   This patch will run with the hardware IDs of both devices.

- Fixed an int promote issue in tmp116_channel_get
  Negative temperature values in drv_data->sample were not
  processed correctly.
  The error occured during integer promotion from u16_t to s32_t
  in this code line:
     tmp = (s32_t)drv_data->sample * TMP116_RESOLUTION;

  By first promoting to s16_t, the correct result is obtained:
     tmp = (s16_t)drv_data->sample * (s32_t)TMP116_RESOLUTION;

- Made temperature resolution compatible to sensor API
  The fractional part of the temperature was returned as a
  multiple of 10^-7 deg.Celsius.
  This differs from the resolution sugegsted by the sensor API,
  which is 10^-6.

  The driver is now returning temperature readings with
  a resolution of 10^-6 deg. Celsius.

- The changed driver was tested using following hardware:
  TMP117 attached to disco_l475_iot1 via i2c1

Signed-off-by: Hans Wilmers <hans@wilmers.no>