rockchip: dts: rk3399-puma: put environment (in MMC/SD configurations) before SPL

As our SPL stage can grow quite large (80KB+ are not unusual) on the
RK3399-Q7, the default setting for the environment location (in
include/configs/rockchip-common.h) can overlap our SPL.

This change finally makes use of the 'u-boot,mmc-env-offset' DTS
property to override the environment location and put it at 16KB into
the device, which is right before the SPL (located at 32KB).

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

arch/arm/dts/rk3399-puma.dtsi

@@ -12,7 +12,8 @@
 	compatible = "tsd,rk3399-q7", "tsd,puma", "rockchip,rk3399";
 
 	config {
-		u-boot,spl-payload-offset = <0x40000>; /* 256kbyte */
+		u-boot,spl-payload-offset = <0x40000>; /* @ 256KB */
+		u-boot,mmc-env-offset = <0x4000>;      /* @  16KB */
 		u-boot,boot-led = "module_led";
 	};