[config] Fix naming of device specific template file

There was a typo in the file name and the name itself does not match
the intent of having defaults packaged with sensorfwd as:
  20-sensor-default.conf

And having device specific overrides derived from
  60-sensors-DEVICE.conf

installed from hw adaptation specific package as something like:
  60-sensor-f5121.conf

Signed-off-by: Simo Piiroinen <simo.piiroinen@jollamobile.com>