Consistently use std::pair<double, double> limits

There are a number of places in tach sensor where we jump from having a
pair of doubles, so having a pair of ints, then back.  All sensors take
this as a double, so we should be consistent, even if tachsensor is only
expected to have integer units.

This was flagged by clang-tidy as part of the
bugprone-misplaced-widening-cast check.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Iee1439f3af2bf8c15dc33f91c63859c5d1b776ca
diff --git a/include/TachSensor.hpp b/include/TachSensor.hpp
index 8dd1b88..75dcd06 100644
--- a/include/TachSensor.hpp
+++ b/include/TachSensor.hpp
@@ -69,7 +69,7 @@
                boost::asio::io_service& io, const std::string& fanName,
                std::vector<thresholds::Threshold>&& thresholds,
                const std::string& sensorConfiguration,
-               const std::pair<size_t, size_t>& limits,
+               const std::pair<double, double>& limits,
                const PowerState& powerState,
                const std::optional<std::string>& led);
     ~TachSensor() override;