xen/evtchn: Remove unused function declaration xen_set_affinity_evtchn()

Commit 67473b81 ("xen/events: Remove disfunct affinity spreading")
leave this unused declaration.
Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Rahul Singh <rahul.singh@arm.com>
Link: https://lore.kernel.org/r/20230801145413.40684-1-yuehaibing@huawei.comSigned-off-by: Juergen Gross <jgross@suse.com>

include/xen/events.h

@@ -75,7 +75,6 @@ void evtchn_put(evtchn_port_t evtchn);
 
 void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector);
 void rebind_evtchn_irq(evtchn_port_t evtchn, int irq);
-int xen_set_affinity_evtchn(struct irq_desc *desc, unsigned int tcpu);
 
 static inline void notify_remote_via_evtchn(evtchn_port_t port)
 {