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/include/spi.h b/include/spi.h
index 6e8e0cc..b714886 100644
--- a/include/spi.h
+++ b/include/spi.h
@@ -80,7 +80,7 @@
  * @mode:	SPI mode to use for this device (see SPI mode flags)
  */
 struct dm_spi_slave_plat {
-	unsigned int cs;
+	unsigned int cs[SPI_CS_CNT_MAX];
 	uint max_hz;
 	uint mode;
 };
@@ -166,6 +166,12 @@
 #define SPI_XFER_ONCE		(SPI_XFER_BEGIN | SPI_XFER_END)
 #define SPI_XFER_U_PAGE		BIT(4)
 #define SPI_XFER_STACKED	BIT(5)
+	/*
+	 * Flag indicating that the spi-controller has multi chip select
+	 * capability and can assert/de-assert more than one chip select
+	 * at once.
+	 */
+	bool multi_cs_cap;
 };
 
 /**