target-i386: Fix including "host" in -cpu ? output
kvm_enabled() cannot be true at this point because accelerators are
initialized much later during init. Also, hiding this makes it very hard
to discover for users. Simply dump unconditionally if CONFIG_KVM is set.
Add explanation for "host" CPU type.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Reviewed-by: Igor Mammedov <imammedo@redhat.com> Signed-off-by: Andreas Färber <afaerber@suse.de>