dm: spi: Correct handling of SPI chip selects in sandbox

This code was not updated when the chip select handling was adjusted. Fix
it to call the correct function.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>
Acked-by: Heiko Schocher <hs@denx.de>

include/spi.h

@@ -533,6 +533,16 @@ int spi_get_bus_and_cs(int busnum, int cs, int speed, int mode,
  */
 int spi_chip_select(struct udevice *slave);
 
+/**
+ * spi_find_chip_select() - Find the slave attached to chip select
+ *
+ * @bus:	SPI bus to search
+ * @cs:		Chip select to look for
+ * @devp:	Returns the slave device if found
+ * @return 0 if found, -ENODEV on error
+ */
+int spi_find_chip_select(struct udevice *bus, int cs, struct udevice **devp);
+
 /**
  * spi_bind_device() - bind a device to a bus's chip select
  *