sfc: Implement asynchronous MCDI requests

This will allow use of MCDI from the data path, in particular for
accelerated RFS.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index db2f119..69150fa 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -1368,6 +1368,9 @@
 		if (!channel->type->keep_eventq)
 			efx_fini_eventq(channel);
 	}
+
+	/* Flush the asynchronous MCDI request queue */
+	efx_mcdi_flush_async(efx);
 }
 
 static void efx_enable_interrupts(struct efx_nic *efx)