doc: lion_rk3368: use idbloader.img for rk3368

Makefile now produces ready-to-deploy idbloader.img file.

Signed-off-by: Matwey V. Kornilov <matwey.kornilov@gmail.com>
Reviewed-by: Kever Yang<kever.yang@rock-chips.com>
diff --git a/board/theobroma-systems/lion_rk3368/README b/board/theobroma-systems/lion_rk3368/README
index 83e4332..ad3ac93 100644
--- a/board/theobroma-systems/lion_rk3368/README
+++ b/board/theobroma-systems/lion_rk3368/README
@@ -18,8 +18,6 @@
 =======================
 
   > make CROSS_COMPILE=aarch64-unknown-elf- ARCH=arm
-  > tools/mkimage -n rk3368 -T rksd -d tpl/u-boot-tpl.bin spl-3368.img
-  > cat spl/u-boot-spl-dtb.bin >> spl-3368.img
 
 Build the full U-Boot and a FIT image including the ATF
 =======================================================
@@ -35,7 +33,7 @@
 SD-Card
 -------
 
-  > dd if=spl-3368.img of=/dev/sdb seek=64
+  > dd if=idbloader.img of=/dev/sdb seek=64
   > dd if=u-boot.itb of=/dev/sdb seek=512
 
 eMMC