KVM: x86: Stop compiling vmenter.S with OBJECT_FILES_NON_STANDARD

KVM: x86: Stop compiling vmenter.S with OBJECT_FILES_NON_STANDARD

Stop compiling vmenter.S with OBJECT_FILES_NON_STANDARD to skip objtool's
stack validation now that __svm_vcpu_run() and __svm_sev_es_vcpu_run()
create stack frames (though the former's effectiveness is dubious).

Note, due to a quirk in how OBJECT_FILES_NON_STANDARD was handled by the
build system prior to commit bf48d9b756b9 ("kbuild: change tool coverage
variables to take the path relative to $(obj)"), vmx/vmenter.S got lumped
in with svm/vmenter.S.  __vmx_vcpu_run() already plays nice with frame
pointers, i.e. it was collateral damage when commit 7f4b5cde2409 ("kvm:
Disable objtool frame pointer checking for vmenter.S") added the
OBJECT_FILES_NON_STANDARD hack-a-fix.

Link: https://lore.kernel.org/all/20240217055504.2059803-1-masahiroy@kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20240223204233.3337324-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>