types: Convert ScaledOffset to double

ScaledOffset is derived from incoming int64 using pow() and there
is a use case for having a fractional or negative ScaledOffset.
Since it's derived internally and applied internally this change
should have no impact on external interfaces.

Change-Id: I419e4de089d3845295157fff440c5d8e029e7c96
Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Tested: Ran ipmitool sensor list to check value sanity
diff --git a/types.hpp b/types.hpp
index 431d5b6..70f397c 100644
--- a/types.hpp
+++ b/types.hpp
@@ -116,7 +116,7 @@
 using Multiplier = uint16_t;
 using OffsetB = int16_t;
 using Exponent = int8_t;
-using ScaledOffset = int64_t;
+using ScaledOffset = double;
 using Scale = int16_t;
 using Unit = std::string;
 using EntityType = uint8_t;