sfc: Use kzalloc() to ensure struct efx_spi_device is fully initialised

Currently the mtd field is not initialised early enough.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/sfc/falcon.c b/drivers/net/sfc/falcon.c
index df844de..6884dc8 100644
--- a/drivers/net/sfc/falcon.c
+++ b/drivers/net/sfc/falcon.c
@@ -2690,7 +2690,7 @@
 	struct efx_spi_device *spi_device;
 
 	if (device_type != 0) {
-		spi_device = kmalloc(sizeof(*spi_device), GFP_KERNEL);
+		spi_device = kzalloc(sizeof(*spi_device), GFP_KERNEL);
 		if (!spi_device)
 			return -ENOMEM;
 		spi_device->device_id = device_id;