ARM: dts: rockchip: Fix rk3288-rock2 vcc_flash name

There is no functional change from this, but it is confusing to find two
copies of vcc_sys and no vcc_flash when looking in
/sys/class/regulator/*/name.
Signed-off-by: John Keeping <john@metanate.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm/boot/dts/rk3288-rock2-som.dtsi

@@ -25,7 +25,7 @@ ext_gmac: external-gmac-clock {
 
 	vcc_flash: flash-regulator {
 		compatible = "regulator-fixed";
-		regulator-name = "vcc_sys";
+		regulator-name = "vcc_flash";
 		regulator-min-microvolt = <1800000>;
 		regulator-max-microvolt = <1800000>;
 		startup-delay-us = <150>;