x86, cpu: Print AMD virtualization features in /proc/cpuinfo

This patch adds code to cpu initialization path to detect
the extended virtualization features of AMD cpus to show
them in /proc/cpuinfo.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
LKML-Reference: <1260792521-15212-1-git-send-email-joerg.roedel@amd.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>