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

ui.cpp

@@ -36,14 +36,12 @@
 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/parseint.h>
-#include <android-base/properties.h>
 #include <android-base/strings.h>
-#include <cutils/android_reboot.h>
 #include <minui/minui.h>
 
-#include "common.h"
-#include "roots.h"
 #include "device.h"
+#include "otautil/sysutil.h"
+#include "roots.h"
 
 static constexpr int UI_WAIT_KEY_TIMEOUT_SEC = 120;
 static constexpr const char* BRIGHTNESS_FILE = "/sys/class/leds/lcd-backlight/brightness";