Add a new base CPU model called 'EPYC' to model processors from AMD EPYC
family (which includes EPYC 76xx,75xx,74xx, 73xx and 72xx).

The following features bits have been added/removed compare to Opteron_G5

Added: monitor, movbe, rdrand, mmxext, ffxsr, rdtscp, cr8legacy, osvw,
       fsgsbase, bmi1, avx2, smep, bmi2, rdseed, adx, smap, clfshopt, sha
       xsaveopt, xsavec, xgetbv1, arat

Removed: xop, fma4, tbm

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Tom Lendacky <Thomas.Lendacky@amd.com>
Signed-off-by: NBrijesh Singh <brijesh.singh@amd.com>
Message-Id: <20170815170051.127257-1-brijesh.singh@amd.com>
Reviewed-by: NEduardo Habkost <ehabkost@redhat.com>
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>