spi_flash: Add spi_flash_probe_fdt() to locate SPI by FDT node

This allows us to put the SPI flash chip inside the SPI interface node,
with U-Boot finding the correct bus and chip select automatically.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/misc/cros_ec_spi.c b/drivers/misc/cros_ec_spi.c
index 202acf2..2fc9110 100644
--- a/drivers/misc/cros_ec_spi.c
+++ b/drivers/misc/cros_ec_spi.c
@@ -135,8 +135,7 @@
  */
 int cros_ec_spi_init(struct cros_ec_dev *dev, const void *blob)
 {
-	dev->spi = spi_setup_slave_fdt(blob, dev->parent_node,
-				       dev->cs, dev->max_frequency, 0);
+	dev->spi = spi_setup_slave_fdt(blob, dev->parent_node, dev->node);
 	if (!dev->spi) {
 		debug("%s: Could not setup SPI slave\n", __func__);
 		return -1;