Correct naming of NMI button in BMCSourceSignal

NMISource related properties already moved from "intel-dbus-interface"
to "phospher-dbus-interfaces".

However, the name "FpBtn" is using for "com.intel", not for
"xyz.openbmc_project" that is using "FrontPanelButton" according to
"xyz/openbmc_project/Chassis/Control/NMISource.interface.yaml".

Thus, need to correct this naming to match current design.

Signed-off-by: Tim Lee <timlee660101@gmail.com>
Change-Id: I9629950fbb077ebf59cd3ef14e382fd40a739895

Author: timlee66

src/power_control.cpp

@@ -2196,7 +2196,7 @@ static void setNmiSource()
         "org.freedesktop.DBus.Properties", "Set",
         "xyz.openbmc_project.Chassis.Control.NMISource", "BMCSource",
         std::variant<std::string>{
-            "xyz.openbmc_project.Chassis.Control.NMISource.BMCSourceSignal.FpBtn"});
+            "xyz.openbmc_project.Chassis.Control.NMISource.BMCSourceSignal.FrontPanelButton"});
     // set Enable Property
     nmiSetEnableProperty(true);
 }