[aarch64-port-dev ] RFR: JDK-8184900 AArch64: Fix overflow in immediate cmp instruction

Hi, all For a fastdebug build openjdk in jdk10/hs tree, there is a failed test case (TestOptionsWithRanges) in jtreg. The reason is that the immediate cmp instruction has 12 significant bits. This causes an overflow in TestOptionsWithRanges. With this patch, TestOptionsWithRanges can be passed and there aren't new failed test cases in jtreg. Bug: https://bugs.openjdk.java.net/browse/JDK-8184900 Webrev: http://cr.openjdk.java.net/~yzhang/8184900/webrev.00/ Please help to review it. Regards, Yang