x86/xen: Add Hygon Dhyana support to Xen

To make Xen work on the Hygon platform, reuse AMD's Xen support code
path for Hygon Dhyana CPU.

There are six core performance events counters per thread, so there are
six MSRs for these counters. Also there are four legacy PMC MSRs, they
are aliases of the counters.

In this version, use the legacy and safe version of MSR access. Tested
successfully with VPMU enabled in Xen on Hygon platform by testing with
perf.

Signed-off-by: Pu Wen <puwen@hygon.cn>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: jgross@suse.com
Cc: tglx@linutronix.de
Cc: mingo@redhat.com
Cc: hpa@zytor.com
Cc: x86@kernel.org
Cc: thomas.lendacky@amd.com
Cc: xen-devel@lists.xenproject.org
Link: https://lkml.kernel.org/r/311bf41f08f24550aa6c5da3f1e03a68d3b89dac.1537533369.git.puwen@hygon.cn