rockchip: mkimage: correct spl_size for rk3399

The maximum spl_size for rk3399 is the internal memory size minus
the size used in bootrom (which usually can get from SPL_TEXT_BASE).

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/tools/rkcommon.c b/tools/rkcommon.c
index db2da75..1056ffa 100644
--- a/tools/rkcommon.c
+++ b/tools/rkcommon.c
@@ -76,7 +76,7 @@
 	{ "rk3188", "RK31", 0x8000 - 0x800, true, false },
 	{ "rk3288", "RK32", 0x8000, false, false },
 	{ "rk3328", "RK32", 0x8000 - 0x1000, false, false },
-	{ "rk3399", "RK33", 0x20000, false, true },
+	{ "rk3399", "RK33", 0x30000 - 0x2000, false, true },
 	{ "rv1108", "RK11", 0x1800, false, false},
 };