arm_fpga: Support more CPU clusters

The maximum number of clusters is currently set to 2, which is quite
limiting. As there are FPGA images with 4 clusters, let's increase the
limit to 4.

Change-Id: I9a85ca07ebbd2a018ad9668536d867ad6b75e537
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

plat/arm/board/arm_fpga/fpga_def.h

@@ -18,7 +18,7 @@
  * that are present will still be indexed appropriately regardless of any empty
  * entries in the array used to represent the topology.
  */
-#define FPGA_MAX_CLUSTER_COUNT			2
+#define FPGA_MAX_CLUSTER_COUNT			4
 #define FPGA_MAX_CPUS_PER_CLUSTER		8
 #define FPGA_MAX_PE_PER_CPU			4