pulsensor: do_sample needs to return a value (NULL)
pulsensor: do_sample needs to return a value (NULL)

defect #346

Signed-off-by: Jon Trulson <08664b19c2d4086eb239dd8ec32d593676a5b9e4@ics.com>
Signed-off-by: Mihai Tudor Panu <a27de6130c5d32f5817bf40bb8b348582f37a8af@intel.com>

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