spi: spi-uclass: Read chipselect and restrict capabilities

Read chipselect properties from DT which are populated using 'reg'
property and save it in plat->cs[] array for later use.

Also read multi chipselect capability which is used for
parallel-memories and return errors if they are passed on using DT but
driver is not capable of handling it.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@amd.com>
Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@amd.com>
diff --git a/drivers/spi/omap3_spi.c b/drivers/spi/omap3_spi.c
index 3d82fc7..35bd876 100644
--- a/drivers/spi/omap3_spi.c
+++ b/drivers/spi/omap3_spi.c
@@ -393,7 +393,7 @@
 	struct omap3_spi_priv *priv = dev_get_priv(bus);
 	struct dm_spi_slave_plat *slave_plat = dev_get_parent_plat(dev);
 
-	priv->cs = slave_plat->cs;
+	priv->cs = slave_plat->cs[0];
 	if (!priv->freq)
 		priv->freq = slave_plat->max_hz;
 
@@ -422,7 +422,7 @@
 	struct omap3_spi_priv *priv = dev_get_priv(bus);
 	struct dm_spi_slave_plat *slave_plat = dev_get_parent_plat(dev);
 
-	priv->cs = slave_plat->cs;
+	priv->cs = slave_plat->cs[0];
 	priv->wordlen = wordlen;
 	_omap3_spi_set_wordlen(priv);