sfc: Replace MDIO spinlock with mutex

We never use MDIO in atomic context, so we don't need to spin.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/sfc/efx.c b/drivers/net/sfc/efx.c
index b5a7e91..6338ad8 100644
--- a/drivers/net/sfc/efx.c
+++ b/drivers/net/sfc/efx.c
@@ -1922,7 +1922,7 @@
 	/* Initialise common structures */
 	memset(efx, 0, sizeof(*efx));
 	spin_lock_init(&efx->biu_lock);
-	spin_lock_init(&efx->phy_lock);
+	mutex_init(&efx->mdio_lock);
 	mutex_init(&efx->spi_lock);
 	INIT_WORK(&efx->reset_work, efx_reset_work);
 	INIT_DELAYED_WORK(&efx->monitor_work, efx_monitor);