sensors: ignore min/max in json for D-Bus passive sensor read

min/max values were meant to scale write to be PWM, but were
overloaded in commit 75eb769d351434547899186f73ff70ae00d7934a
to scale sensor read to percent as well. However currently the D-Bus sensors
built from JSON can only specify one pair of min/max values,so they
cannot be used for both read/write interfaces.

Fix the behavior by ignoring min/max in settings when building D-Bus passive
read interface and only read them from D-Bus.

Tested:
  D-Bus passive sensor value is no longer scaled if there is no
  MinValue/MaxValue specified.

Resolves: openbmc/phosphor-pid-control#14

Signed-off-by: Kun Yi <kunyi731@gmail.com>
Change-Id: I206bbe75c77e79f765eca76cfa015321dcba4aa7
diff --git a/conf.hpp b/conf.hpp
index 9d65154..35c2da5 100644
--- a/conf.hpp
+++ b/conf.hpp
@@ -10,8 +10,6 @@
 namespace conf
 {
 
-constexpr int64_t inheritValueFromDbus = std::numeric_limits<int64_t>::lowest();
-
 /*
  * General sensor structure used for configuration.
  */
diff --git a/dbus/dbusconfiguration.cpp b/dbus/dbusconfiguration.cpp
index c33264c..7641eaf 100644
--- a/dbus/dbusconfiguration.cpp
+++ b/dbus/dbusconfiguration.cpp
@@ -527,11 +527,6 @@
                         {
                             config.timeout = 0;
                         }
-                        else if (config.type == "fan")
-                        {
-                            config.max = conf::inheritValueFromDbus;
-                            config.min = conf::inheritValueFromDbus;
-                        }
                     }
                     else if (sensorPathIfacePair.second == pwmInterface)
                     {
diff --git a/dbus/dbuspassive.cpp b/dbus/dbuspassive.cpp
index 5614335..c199563 100644
--- a/dbus/dbuspassive.cpp
+++ b/dbus/dbuspassive.cpp
@@ -60,15 +60,6 @@
     {
         return nullptr;
     }
-    if (info->max != conf::inheritValueFromDbus)
-    {
-        settings.max = info->max;
-    }
-
-    if (info->min != conf::inheritValueFromDbus)
-    {
-        settings.min = info->min;
-    }
 
     return std::make_unique<DbusPassive>(bus, type, id, helper, settings,
                                          failed, path, redundancy);