rockchip: Disable DISTRO_DEFAULTS for rk3399 boards

These board have moved to standard boot but the old 'distro_bootcmd'
command is still active. Disable DISTRO_DEFAULTS to fix this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Vagrant Cascadian <vagrant@debian.org>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index bd7fffc..4e7ebea 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1955,7 +1955,7 @@
 	imply ADC
 	imply CMD_DM
 	imply DEBUG_UART_BOARD_INIT
-	imply DISTRO_DEFAULTS
+	imply DISTRO_DEFAULTS if !ROCKCHIP_RK3399
 	imply FAT_WRITE
 	imply SARADC_ROCKCHIP
 	imply SPL_SYSRESET