ARM64: zynqmp: Add initial support for the first silicon

Add basic configuration for the first silicon.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/arch/arm/cpu/armv8/zynqmp/cpu.c b/arch/arm/cpu/armv8/zynqmp/cpu.c
index 45b49dc..c71f291 100644
--- a/arch/arm/cpu/armv8/zynqmp/cpu.c
+++ b/arch/arm/cpu/armv8/zynqmp/cpu.c
@@ -38,9 +38,11 @@
 		return ZYNQMP_CSU_VERSION_VELOCE;
 	case 50000000:
 		return ZYNQMP_CSU_VERSION_QEMU;
+	case 4000000:
+		return ZYNQMP_CSU_VERSION_EP108;
 	}
 
-	return ZYNQMP_CSU_VERSION_EP108;
+	return ZYNQMP_CSU_VERSION_SILICON;
 }
 
 #ifndef CONFIG_SYS_DCACHE_OFF