Thermistortableless: use sensor-specific vadc.

This is a first test to use sensor-specific values. Works
apparently well.

Code size before:

  FLASH : 20052 bytes          140%       66%        32%       16%
  RAM   :  2195 bytes          215%      108%        54%       27%
  EEPROM:    32 bytes            4%        2%         2%        1%

Code size now:

  FLASH : 20052 bytes          140%       66%        32%       16%
  RAM   :  2201 bytes          215%      108%        54%       27%
  EEPROM:    32 bytes            4%        2%         2%        1%