x86: Add cache information support for Zhaoxin processors

To obtain Zhaoxin CPU cache information, add a new function
handle_zhaoxin().

Add a new function get_common_cache_info() that extracts the code
in init_cacheinfo() to get the value of the variable shared, threads.

Add Zhaoxin branch in init_cacheinfo() for initializing variables,
such as __x86_shared_cache_size.