sfc: Allow event queue initialisation to fail

On EF10, event queue initialisation requires an MCDI request which
may return failure.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
diff --git a/drivers/net/ethernet/sfc/farch.c b/drivers/net/ethernet/sfc/farch.c
index d21483d..904af5c 100644
--- a/drivers/net/ethernet/sfc/farch.c
+++ b/drivers/net/ethernet/sfc/farch.c
@@ -1325,7 +1325,7 @@
 					entries * sizeof(efx_qword_t));
 }
 
-void efx_farch_ev_init(struct efx_channel *channel)
+int efx_farch_ev_init(struct efx_channel *channel)
 {
 	efx_oword_t reg;
 	struct efx_nic *efx = channel->efx;
@@ -1358,6 +1358,8 @@
 			 channel->channel);
 
 	efx->type->push_irq_moderation(channel);
+
+	return 0;
 }
 
 void efx_farch_ev_fini(struct efx_channel *channel)