Move reboot() from common.h into otautil/sysutil.h.

This breaks the dependency on common.h (which belongs to
recovery/librecovery) from librecovery_ui. reboot() is now owned by
libotautil, which is expected to be a leaf node to be depended on.

With the change, recovery and updater also share the same reboot() code
now.

Test: mmma -j bootable/recovery
Change-Id: I1cc5d702cfe49302048db33d31c9c87ddc97ac71
diff --git a/Android.mk b/Android.mk
index acff24a..abe1b83 100644
--- a/Android.mk
+++ b/Android.mk
@@ -65,6 +65,7 @@
 
 LOCAL_STATIC_LIBRARIES := \
     libminui \
+    libotautil \
     libbase
 
 ifneq ($(TARGET_RECOVERY_UI_MARGIN_HEIGHT),)