ensure proper data type for variant
ensure proper data type for variant

gcc10 is more strict on variant usage

Signed-off-by: Andrew Geissler <f7919ac9f8ec0c3ffbc3f483da625c634fd31638@yahoo.com>
Change-Id: I906d1710312cad907ed5db5c04d9b1aec101fca4

openbmc/phosphor-pid-control,openbmc/phosphor-pid-control