rockchip: rk3399: defconfig: remove SPL raw image support

RK3399 SPL only support FIT image for ATF bl31.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/configs/firefly-rk3399_defconfig b/configs/firefly-rk3399_defconfig
index 38ac8a3..d022631 100644
--- a/configs/firefly-rk3399_defconfig
+++ b/configs/firefly-rk3399_defconfig
@@ -11,6 +11,7 @@
 CONFIG_DEFAULT_FDT_FILE="rockchip/rk3399-firefly.dtb"
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y
+# CONFIG_SPL_RAW_IMAGE_SUPPORT is not set
 CONFIG_SPL_STACK_R=y
 CONFIG_SPL_STACK_R_MALLOC_SIMPLE_LEN=0x10000
 CONFIG_TPL=y