target/i386: Expose new feature bits in CPUID 8000_0021_EAX/EBX

target/i386: Expose new feature bits in CPUID 8000_0021_EAX/EBX

Newer AMD CPUs support ERAPS (Enhanced Return Address Prediction Security)
feature that enables the auto-clear of RSB entries on a TLB flush, context
switches and VMEXITs. The number of default RSP entries is reflected in
RapSize.

Add the feature bit and feature word to support these features.

CPUID_Fn80000021_EAX
Bits   Feature Description
24     ERAPS:
       Indicates support for enhanced return address predictor security.

CPUID_Fn80000021_EBX
Bits   Feature Description
31-24  Reserved
23:16  RapSize:
       Return Address Predictor size. RapSize x 8 is the minimum number
       of CALL instructions software needs to execute to flush the RAP.
15-00  MicrocodePatchSize. Read-only.
       Reports the size of the Microcode patch in 16-byte multiples.
       If 0, the size of the patch is at most 5568 (15C0h) bytes.

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>
Link: https://lore.kernel.org/r/7c62371fe60af1e9bbd853f5f8e949bf2d908bd0.1729807947.git.babu.moger@amd.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>