KVM: x86: Add a macro to init CPUID features that KVM emulates in software

KVM: x86: Add a macro to init CPUID features that KVM emulates in software

Now that kvm_cpu_cap_init() is a macro with its own scope, add EMUL_F() to
OR-in features that KVM emulates in software, i.e. that don't depend on
the feature being available in hardware.  The contained scope
of kvm_cpu_cap_init() allows using a local variable to track the set of
emulated leaves, which in addition to avoiding confusing and/or
unnecessary variables, helps prevent misuse of EMUL_F().

Link: https://lore.kernel.org/r/20241128013424.4096668-31-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>