dm: spi: Convert uclass to livetree

Update the SPI uclass to support a live device tree. Also adjust
spi_slave_ofdata_to_platdata() to accept a device instead of a blob and
offset.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/spi.h b/include/spi.h
index deb65ef..8c4b882 100644
--- a/include/spi.h
+++ b/include/spi.h
@@ -562,7 +562,7 @@
  * @node:	Node offset to read from
  * @plat:	Place to put the decoded information
  */
-int spi_slave_ofdata_to_platdata(const void *blob, int node,
+int spi_slave_ofdata_to_platdata(struct udevice *dev,
 				 struct dm_spi_slave_platdata *plat);
 
 /**