KVM: Drop __KVM_HAVE_IOAPIC condition on irq routing

We have a capability enquire system that allows user space to ask kvm
whether a feature is available.

The point behind this system is that we can have different kernel
configurations with different capabilities and user space can adjust
accordingly.

Because features can always be non existent, we can drop any #ifdefs
on CAP defines that could be used generically, like the irq routing
bits. These can be easily reused for non-IOAPIC systems as well.

Signed-off-by: Alexander Graf <agraf@suse.de>
Acked-by: Michael S. Tsirkin <mst@redhat.com>