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/mxc_spi.c b/drivers/spi/mxc_spi.c
index e7c393a..9ab39a1 100644
--- a/drivers/spi/mxc_spi.c
+++ b/drivers/spi/mxc_spi.c
@@ -135,7 +135,7 @@
 	struct udevice *dev = mxcs->dev;
 	struct dm_spi_slave_plat *slave_plat = dev_get_parent_plat(dev);
 
-	u32 cs = slave_plat->cs;
+	u32 cs = slave_plat->cs[0];
 
 	if (!dm_gpio_is_valid(&mxcs->cs_gpios[cs]))
 		return;
@@ -153,7 +153,7 @@
 	struct udevice *dev = mxcs->dev;
 	struct dm_spi_slave_plat *slave_plat = dev_get_parent_plat(dev);
 
-	u32 cs = slave_plat->cs;
+	u32 cs = slave_plat->cs[0];
 
 	if (!dm_gpio_is_valid(&mxcs->cs_gpios[cs]))
 		return;
@@ -632,7 +632,7 @@
 
 	mxcs->dev = dev;
 
-	return mxc_spi_claim_bus_internal(mxcs, slave_plat->cs);
+	return mxc_spi_claim_bus_internal(mxcs, slave_plat->cs[0]);
 }
 
 static int mxc_spi_release_bus(struct udevice *dev)