KVM: x86: Limit use of F() and SF() to kvm_cpu_cap_{mask,init_kvm_defined}()

KVM: x86: Limit use of F() and SF() to kvm_cpu_cap_{mask,init_kvm_defined}()

Define and undefine the F() and SF() macros precisely around
kvm_set_cpu_caps() to make it all but impossible to use the macros outside
of kvm_cpu_cap_{mask,init_kvm_defined}().  Currently, F() is a simple
passthrough, but SF() is actively dangerous as it checks that the scattered
feature is supported by the host kernel.

And usage outside of the aforementioned helpers will run afoul of future
changes to harden KVM's CPUID management.

Opportunistically switch to feature_bit() when stuffing LA57 based on raw
hardware support.

No functional change intended.

Link: https://lore.kernel.org/r/20241128013424.4096668-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>