KVM: x86: Consolidate CPUID fault handling for emulator and interception logic

KVM: x86: Consolidate CPUID fault handling for emulator and interception logic

Extract the logic for emulating CPUID faulting (where CPUID #GPs at CPL>0
outside of SMM) into a dedicated helper and use the helper for both the
full emulator and the intercepted-CPUID paths.

Opportunistically drop kvm_require_cpl(), as kvm_emulate_cpuid() was the
one and only user.

No functional change intended.

[jim: Add EXPORT_STATIC_CALL_GPL(kvm_x86_get_cpl) so that KVM vendor
modules can call kvm_is_cpuid_allowed(). Fix typo in commit message.]

Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://patch.msgid.link/20260527174347.2356165-2-jmattson@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>