refactor(fvp): fdts: consolidate GICv3 base FVP DT files

The GICv2 and GICv3 version of the FVP DT files are unnecessarily split,
as the common part of the peripherals is the same: it's literally just
the interrupt controller node that is different.
To facilitate a unification, refactor the DT include files to explicitly
include a snippet with just the GICv3 description, and a generic base DT
file for the rest. This generic file can then be reused by the GICv2
versions later.

Since we can only have a /memreserve/ entry *before* any DT nodes, move
that line to each file, to allow including the GIC DT file separately.

Change-Id: I9ff357d3fe0ce46e280c30131aeae97a99631512
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/fdts/fvp-base-gicv3-psci-1t.dts b/fdts/fvp-base-gicv3-psci-1t.dts
index c5e0424..829555b 100644
--- a/fdts/fvp-base-gicv3-psci-1t.dts
+++ b/fdts/fvp-base-gicv3-psci-1t.dts
@@ -6,9 +6,13 @@
 
 /* Configuration: max 4 clusters with up to 4 CPUs with 1 thread per each */
 
-/dts-v1/;
-
 #define	AFF	00
 
 #include "fvp-defs.dtsi"
-#include "fvp-base-gicv3-psci-common.dtsi"
+
+/dts-v1/;
+
+/memreserve/ 0x80000000 0x00010000;
+
+#include "fvp-base-gicv3.dtsi"
+#include "fvp-base-psci-common.dtsi"