i386: Add 2nd Generation AMD EPYC processors

Adds the support for 2nd Gen AMD EPYC Processors. The model display
name will be EPYC-Rome.

Adds the following new feature bits on top of the feature bits from the
first generation EPYC models.
perfctr-core : core performance counter extensions support. Enables the VM to
               use extended performance counter support. It enables six
               programmable counters instead of four counters.
clzero       : instruction zeroes out the 64 byte cache line specified in RAX.
xsaveerptr   : XSAVE, XSAVE, FXSAVEOPT, XSAVEC, XSAVES always save error
               pointers and FXRSTOR, XRSTOR, XRSTORS always restore error
               pointers.
wbnoinvd     : Write back and do not invalidate cache
ibpb         : Indirect Branch Prediction Barrier
amd-stibp    : Single Thread Indirect Branch Predictor
clwb         : Cache Line Write Back and Retain
xsaves       : XSAVES, XRSTORS and IA32_XSS support
rdpid        : Read Processor ID instruction support
umip         : User-Mode Instruction Prevention support

The  Reference documents are available at
https://developer.amd.com/wp-content/resources/55803_0.54-PUB.pdf
https://www.amd.com/system/files/TechDocs/24594.pdf



Depends on following kernel commits:
40bc47b08b6e ("kvm: x86: Enumerate support for CLZERO instruction")
504ce1954fba ("KVM: x86: Expose XSAVEERPTR to the guest")
6d61e3c32248 ("kvm: x86: Expose RDPID in KVM_GET_SUPPORTED_CPUID")
52297436199d ("kvm: svm: Update svm_xsaves_supported")

Signed-off-by: Babu Moger <babu.moger@amd.com>
Message-Id: <157314966312.23828.17684821666338093910.stgit@naples-babu.amd.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>