libpldmresponder: Add double property type for D-Bus backend

Add a handler with double property type in the get/setAttrValue methods.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I493678b57199e8f7c252da99292029f77eef482e
diff --git a/libpldmresponder/bios_integer_attribute.cpp b/libpldmresponder/bios_integer_attribute.cpp
index 23ffab3..d6d1214 100644
--- a/libpldmresponder/bios_integer_attribute.cpp
+++ b/libpldmresponder/bios_integer_attribute.cpp
@@ -87,6 +87,11 @@
         return dbusHandler->setDbusProperty(*dBusMap,
                                             static_cast<int64_t>(currentValue));
     }
+    else if (dBusMap->propertyType == "double")
+    {
+        return dbusHandler->setDbusProperty(*dBusMap,
+                                            static_cast<double>(currentValue));
+    }
 
     std::cerr << "Unsupported property type on dbus: " << dBusMap->propertyType
               << std::endl;
@@ -146,6 +151,10 @@
     {
         value = std::get<int64_t>(propertyValue);
     }
+    else if (dBusMap->propertyType == "double")
+    {
+        value = std::get<double>(propertyValue);
+    }
     return value;
 }