toolbox: add "uptime" command

Prints elapsed real time since boot, as well as idle time and sleep time.

Change-Id: I97f482d6087e9f802d74e91147bf767e6b2d4f42
Signed-off-by: Mike Lockwood <lockwood@android.com>
diff --git a/toolbox/Android.mk b/toolbox/Android.mk
index a6114ac..5f72311 100644
--- a/toolbox/Android.mk
+++ b/toolbox/Android.mk
@@ -52,7 +52,8 @@
 	id \
 	vmstat \
 	nandread \
-        ionice
+	uptime \
+	ionice
 
 LOCAL_SRC_FILES:= \
 	toolbox.c \