use stoll() to convert threshold string to number
use stoll() to convert threshold string to number

The stoi() and stol() functions will throw out of range
exceptions when trying to convert valid threshold values,
such as power numbers in microwatts.

Change-Id: Ifd4c12fb37d6bd905c73633a468f35361b544fa7
Signed-off-by: Matt Spinler <c000c989d08c98662d98f15448f11de169feb92d@us.ibm.com>

openbmc/phosphor-hwmon,openbmc/phosphor-hwmon