spl: Init proper struct driver member (platdata_auto_alloc_size) for mxs_spi

This change initializes proper member of struct driver -
platdata_auto_alloc_size instead of priv_auto_alloc_size, which is setup
twice.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
diff --git a/drivers/spi/mxs_spi.c b/drivers/spi/mxs_spi.c
index 3a9756f..b1cc83a 100644
--- a/drivers/spi/mxs_spi.c
+++ b/drivers/spi/mxs_spi.c
@@ -584,7 +584,7 @@
 	.of_match = mxs_spi_ids,
 	.ofdata_to_platdata = mxs_ofdata_to_platdata,
 #endif
-	.priv_auto_alloc_size = sizeof(struct mxs_spi_platdata),
+	.platdata_auto_alloc_size = sizeof(struct mxs_spi_platdata),
 	.ops	= &mxs_spi_ops,
 	.priv_auto_alloc_size = sizeof(struct mxs_spi_priv),
 	.probe	= mxs_spi_probe,