sensor: to enable testing receive hwmonio interface pointer

The sensor objects all share a reference to the mainloop's ioAccess
object.  To enable testing, the sensor object needs to expect the base
pointer to this object.

Change-Id: I1d7f2841528776c8d4f1166e20874ddeb4b8554a
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/mainloop.cpp b/mainloop.cpp
index 29bd378..b6d44b7 100644
--- a/mainloop.cpp
+++ b/mainloop.cpp
@@ -148,8 +148,9 @@
         return {};
     }
 
+    /* Note: The sensor objects all share the same ioAccess object. */
     auto sensorObj =
-        std::make_unique<sensor::Sensor>(sensor.first, ioAccess, _devPath);
+        std::make_unique<sensor::Sensor>(sensor.first, &ioAccess, _devPath);
 
     // Get list of return codes for removing sensors on device
     auto devRmRCs = env::getEnv("REMOVERCS");