Enable ROCKCHIP_SPL_BACK_TO_BROM for rock2 board

Rock2 has been tested with back to brom feature. The tricky part is that
with this feature the default environment is inside u-boot, and it's
defined for every rk3288 board independetly. So I just changed it for
rock2 here if ROCKCHIP_SPL_BACK_TO_BROM.

Solve by moving environment after u-boot before 1M boundary

Signed-off-by: Sandy Patterson <apatterson@sightlogix.com>
Acked-by: Simon Glass <sjg@chromium.org>

configs/rock2_defconfig

@@ -7,6 +7,8 @@ CONFIG_SPL_STACK_R_ADDR=0x80000
 CONFIG_DEFAULT_DEVICE_TREE="rk3288-rock2-square"
 CONFIG_SPL_STACK_R=y
 CONFIG_SPL_STACK_R_MALLOC_SIMPLE_LEN=0x2000
+# CONFIG_SPL_MMC_SUPPORT is not set
+CONFIG_ROCKCHIP_SPL_BACK_TO_BROM=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMLS is not set

include/configs/rock2.h

@@ -16,11 +16,20 @@
 
 #define CONFIG_ENV_IS_IN_MMC
 #define CONFIG_SYS_MMC_ENV_DEV 0
+
+#ifdef CONFIG_ROCKCHIP_SPL_BACK_TO_BROM
+/* SPL @ 32k for 34k
+ * u-boot directly after @ 68k for 400k or so
+ * ENV @ 992k
+ */
+#define CONFIG_ENV_OFFSET ((1024-32) * 1024)
+#else
 /* SPL @ 32k for ~36k
  * ENV @ 96k
  * u-boot @ 128K
  */
 #define CONFIG_ENV_OFFSET (96 * 1024)
+#endif
 
 #define CONFIG_SYS_WHITE_ON_BLACK
 #define CONFIG_CONSOLE_SCROLL_LINES		10