MIPS: Loongson-2F: Flush the branch target history in BTB and RAS
As per chapter 15 "Errata: Issue of Out-of-order in loongson"[1] to work
around the Loongson 2F erratum we need to do:
"When switching from user mode to kernel mode, you should flush the
branch target history such as BTB and RAS."
[1] Chinese version: http://www.loongson.cn/uploadfile/file/
200808211
[2] English version of chapter 15:
http://groups.google.com.hk/group/loongson-dev/msg/
e0d2e220958f10a6?dmode=source
Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: Shinya Kuribayashi <shinya.kuribayashi@necel.com>
Patchwork: http://patchwork.linux-mips.org/patch/1066/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>