bmc: implement reboot update mechanism

Implement an update mechanism that simply triggers a reboot of the BMC.
This implementation isn't tied into anything in the firmware handler
yet.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I116d4f631a44e7a4a999cf8ad403a00935f58710
diff --git a/Makefile.am b/Makefile.am
index cc7f110..6e03b0a 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -43,7 +43,8 @@
 	firmware_handler.cpp \
 	file_handler.cpp \
 	internal/sys.cpp \
-	verify_systemd.cpp
+	verify_systemd.cpp \
+	update_systemd.cpp
 
 if ENABLE_LPC_BRIDGE
 libfirmwareblob_common_la_SOURCES += lpc_handler.cpp