Support multi power buttons with multi behaviors

For supporting more-than-one power buttons behaviors,
add new matches and instances by following json config.

This change is for multiple slots integrated on one chassis,
and each slot has button to control power status.

For example:
/xyz/openbmc_project/Chassis/Buttons/Power01 for button on slot1
/xyz/openbmc_project/Chassis/Buttons/Power02 for button on slot2

Moreover, support multi-level power control by json config,
chassis now can do action by corresponding pressing duration.

Tested:
Press buttons and check corresponding behaviors.

Change-Id: I7789f0367d5e846dd9e68f966ba0755fc916217a
Signed-off-by: Rush Chen <rush.chen.wiwynn@gmail.com>
diff --git a/src/power_button.cpp b/src/power_button.cpp
index 80334a8..879c659 100644
--- a/src/power_button.cpp
+++ b/src/power_button.cpp
@@ -16,8 +16,11 @@
 
 #include "power_button.hpp"
 
+#include "button_handler.hpp"
+
 // add the button iface class to registry
-static ButtonIFRegister<PowerButton> buttonRegister;
+static ButtonIFRegister<PowerButton>
+    multiButtonRegister(phosphor::button::numberOfChassis());
 
 void PowerButton::simPress()
 {