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/spi-synquacer.c b/drivers/spi/spi-synquacer.c
index eb522fd..a3c0ad1 100644
--- a/drivers/spi/spi-synquacer.c
+++ b/drivers/spi/spi-synquacer.c
@@ -193,12 +193,12 @@
 	/* if nothing to do */
 	if (slave_plat->mode == priv->mode &&
 	    rwflag == priv->rwflag &&
-	    slave_plat->cs == priv->cs &&
+	    slave_plat->cs[0] == priv->cs &&
 	    slave_plat->max_hz == priv->speed)
 		return;
 
 	priv->rwflag = rwflag;
-	priv->cs = slave_plat->cs;
+	priv->cs = slave_plat->cs[0];
 	priv->mode = slave_plat->mode;
 	priv->speed = slave_plat->max_hz;