ARM64: dts: meson-gxl: Add alternate ARM Trusted Firmware reserved memory zone

This year, Amlogic updated the ARM Trusted Firmware reserved memory mapping
for Meson GXL SoCs and products sold since May 2017 uses this alternate
reserved memory mapping.
But products had been sold using the previous mapping.

This issue has been explained in [1] and a dynamic solution is yet to be
found to avoid loosing another 3Mbytes of reservable memory.

In the meantime, this patch adds this alternate memory zone only for
the GXL and GXM SoCs since GXBB based new products stopped earlier.

[1] http://lists.infradead.org/pipermail/linux-amlogic/2017-October/004860.html

Fixes: bba8e3f4 ("ARM64: dts: meson-gx: Add firmware reserved memory zones")
Reported-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

arch/arm64/boot/dts/amlogic/meson-gxl.dtsi

@@ -49,6 +49,14 @@
 
 / {
 	compatible = "amlogic,meson-gxl";
+
+	reserved-memory {
+		/* Alternate 3 MiB reserved for ARM Trusted Firmware (BL31) */
+		secmon_reserved_alt: secmon@05000000 {
+			reg = <0x0 0x05000000 0x0 0x300000>;
+			no-map;
+		};
+	};
 };
 
 &ethmac {