side-switch: power off chassis in prep for update

When switching to a new level of firmware, ensure the host is off and
the chassis power is off before switching to the new firmware.

Tested:
- Verify power off works
<6> Checking for side switch reboot
<6> Running firmware version path is /xyz/openbmc_project/software/74575136
<6> Running firmware version priority is 1
<6> Running image is at priority 1, execute side switch
<see power off occur in journal>
<6> chassis power is off

Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: Ifdb3e0c51fe66e55ebb1c3fca7097af49607bf35
diff --git a/side-switch/side_switch.hpp b/side-switch/side_switch.hpp
index 684cae9..4af52cb 100644
--- a/side-switch/side_switch.hpp
+++ b/side-switch/side_switch.hpp
@@ -1,7 +1,17 @@
 #pragma once
 
+#include <sdbusplus/bus.hpp>
+
 /** @brief Determine if a side switch is needed
  *
+ *  @param[in] bus       - The Dbus bus object
  *  @return True if side switch needed, false otherwise
  */
-bool sideSwitchNeeded();
+bool sideSwitchNeeded(sdbusplus::bus::bus& bus);
+
+/** @brief Power off the system
+ *
+ *  @param[in] bus       - The Dbus bus object
+ *  @return True if chassis off success, false otherwise
+ */
+bool powerOffSystem(sdbusplus::bus::bus& bus);