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>
1 file changed