target/i386: Add couple of feature bits in CPUID_Fn80000021_EAX

target/i386: Add couple of feature bits in CPUID_Fn80000021_EAX

Add CPUID bit indicates that a WRMSR to MSR_FS_BASE, MSR_GS_BASE, or
MSR_KERNEL_GS_BASE is non-serializing amd PREFETCHI that the indicates
support for IC prefetch.

CPUID_Fn80000021_EAX
Bit    Feature description
20     Indicates support for IC prefetch.
1      FsGsKernelGsBaseNonSerializing.
       WRMSR to FS_BASE, GS_BASE and KernelGSbase are non-serializing.

Link: https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/programmer-references/57238.zip
Signed-off-by: Babu Moger <babu.moger@amd.com>
Reviewed-by: Maksim Davydov <davydov-max@yandex-team.ru>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/a5f6283a59579b09ac345b3f21ecb3b3b2d92451.1746734284.git.babu.moger@amd.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>