x86/speculation/swapgs: Exclude Zhaoxin CPUs from SWAPGS vulnerability

New Zhaoxin family 7 CPUs are not affected by the SWAPGS vulnerability. So
mark these CPUs in the cpu vulnerability whitelist accordingly.

Signed-off-by: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1579227872-26972-3-git-send-email-TonyWWang-oc@zhaoxin.com