rockchip: dts: rk3399-puma: add DTS for the DDR3-1866 timing

This adds the DDR3-1866 timing via its own DTS and wires it up.  This
(currently) is not the default timing for the RK3399-Q7 and should be
selected explicitly via the config (CONFIG_DEFAULT_DEVICE_TREE).

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index 540fa25..8b8f5e9 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -48,6 +48,7 @@
 	rk3399-firefly.dtb \
 	rk3399-puma-ddr1333.dtb \
 	rk3399-puma-ddr1600.dtb \
+	rk3399-puma-ddr1866.dtb \
 	rv1108-evb.dtb
 dtb-$(CONFIG_ARCH_MESON) += \
 	meson-gxbb-odroidc2.dtb