Add support for Hygon Dhyana processor

Add support for Hygon Dhyana processor

-Add vendor identification
-Support in get_cpu_cache

Background:
    Chengdu Haiguang IC Design Co., Ltd (Hygon) is a Joint Venture
    between AMD and Haiguang Information Technology Co.,Ltd., aims at
    providing high performance x86 processor for China server market.
    Its first generation processor codename is Dhyana, which
    originates from AMD technology and shares most of the
    architecture with AMD's family 17h, but with different CPU Vendor
    ID("HygonGenuine")/Family series number(Family 18h).

Related Hygon kernel patch can be found on:
http://lkml.kernel.org/r/5ce86123a7b9dad925ac583d88d2f921040e859b.1538583282.git.puwen@hygon.cn

Signed-off-by: Jinke Fan <fanjinke@hygon.cn>