efi_loader: RegisterProtocolNotify event signaling

In a following patch efi_signal_event() will only queue an event if it is
not signaled.

Set the is_signaled status to false before signaling the event.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

lib/efi_loader/efi_boottime.c

@@ -1068,6 +1068,7 @@ efi_status_t efi_add_protocol(const efi_handle_t handle,
 			}
 			notif->handle = handle;
 			list_add_tail(&notif->link, &event->handles);
+			event->event->is_signaled = false;
 			efi_signal_event(event->event, true);
 		}
 	}