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>
diff --git a/include/spi.h b/include/spi.h
index aa0a48e..5975cda 100644
--- a/include/spi.h
+++ b/include/spi.h
@@ -534,6 +534,16 @@
 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
  *
  * This binds a new device to an given chip select (which must be unused).