rockchip: Add support for rk's second level loader

The Rockchip boot ROM could load & run an initial spl loader,
and continue to load a second level boot-loader(which stored
right after the initial loader) when it returns.
Modify idblock generation code to support it.

Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Acked-by: Simon Glass <sjg@chromium.org>

tools/rkcommon.h

@@ -10,7 +10,8 @@
 
 enum {
 	RK_BLK_SIZE		= 512,
-	RK_CODE1_OFFSET		= 4,
+	RK_INIT_OFFSET		= 4,
+	RK_MAX_BOOT_SIZE	= 512 << 10,
 };
 
 /**