drivers: xen: export missing evtchn API function

Previously clear_event_channel() function, that is a part of Xen event
channel API was missing in events.h header.

Add function declaration and documentation description for to let users
add it to external drivers.

Signed-off-by: Dmytro Firsov <dmytro_firsov@epam.com>

Author: firscity

drivers/xen/events.c

@@ -197,7 +197,7 @@ int unmask_event_channel(evtchn_port_t port)
 	return 0;
 }
 
-static void clear_event_channel(evtchn_port_t port)
+void clear_event_channel(evtchn_port_t port)
 {
 	shared_info_t *s = HYPERVISOR_shared_info;
 

include/zephyr/xen/events.h

@@ -81,6 +81,12 @@ int get_missed_events(evtchn_port_t port);
 int mask_event_channel(evtchn_port_t port);
 int unmask_event_channel(evtchn_port_t port);
 
+/**
+ * Clear event channel from pending events
+ * @param port - event channel number
+ */
+void clear_event_channel(evtchn_port_t port);
+
 int xen_events_init(void);
 
 #endif /* __XEN_EVENTS_H__ */