sfc: Warn if unable to create MTDs

Log an explicit warning if we are unable to create MTDs for a net
device.  Also correct the comment about why mtd_device_register() may
fail; there is no longer an MTD table to fill up.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
diff --git a/drivers/net/ethernet/sfc/mtd.c b/drivers/net/ethernet/sfc/mtd.c
index 79c1922..26b3c23 100644
--- a/drivers/net/ethernet/sfc/mtd.c
+++ b/drivers/net/ethernet/sfc/mtd.c
@@ -280,7 +280,7 @@
 		--part;
 		efx_mtd_remove_partition(part);
 	}
-	/* mtd_device_register() returns 1 if the MTD table is full */
+	/* Failure is unlikely here, but probably means we're out of memory */
 	return -ENOMEM;
 }