KVM: x86: Use only local variables (no bitmask) to init kvm_cpu_caps

Refactor the kvm_cpu_cap_init() macro magic to collect supported features
in a local variable instead of passing them to the macro as a "mask".  As
pointed out by Maxim, relying on macros to "return" a value and set local
variables is surprising, as the bitwise-OR logic suggests the macros are
pure, i.e. have no side effects.

Ideally, the feature initializers would have zero side effects, e.g. would
take local variables as params, but there isn't a sane way to do so
without either sacrificing the various compile-time assertions (basically
a non-starter), or passing at least one variable, e.g. a struct, to each
macro usage (adds a lot of noise and boilerplate code).

Opportunistically force callers to emit a trailing comma by intentionally
omitting a semicolon after invoking the feature initializers.  Forcing a
trailing comma isotales futures changes to a single line, i.e. doesn't
cause churn for unrelated features/lines when adding/removing/modifying a
feature.

No functional change intended.

Suggested-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-58-seanjc@google.com


Signed-off-by: Sean Christopherson <seanjc@google.com>