spi: ich: Move the protection/lockdown code into a function

Reduce the size of the probe function but putting this code into its own
function.

Also remove the assumption that the PCH is always a parent of the SPI
controller, as this is not the case APL platforms. Use driver model to
find the PCH instead.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/spi/ich.h b/drivers/spi/ich.h
index 3dfb2aa..7705787 100644
--- a/drivers/spi/ich.h
+++ b/drivers/spi/ich.h
@@ -191,6 +191,7 @@
 	ulong max_speed;	/* Maximum bus speed in MHz */
 	ulong cur_speed;	/* Current bus speed */
 	struct spi_trans trans;	/* current transaction in progress */
+	struct udevice *pch;	/* PCH, used to control SPI access */
 };
 
 #endif /* _ICH_H_ */