feat(rdn2): add platform id value for rdn2 variant 3

The RD-N2-Cfg3 platform is a variant of the RD-N2 platform with the
significant difference being the number of ITS blocks and the use of a
different part number.

Signed-off-by: Tony K Nadackal <tony.nadackal@arm.com>
Change-Id: Id4c5faeae44f21da79cb59540558192d0b02b124
diff --git a/plat/arm/css/sgi/include/sgi_variant.h b/plat/arm/css/sgi/include/sgi_variant.h
index 223ac3e..8f9529a 100644
--- a/plat/arm/css/sgi/include/sgi_variant.h
+++ b/plat/arm/css/sgi/include/sgi_variant.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2022, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2018-2023, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -22,6 +22,7 @@
 
 /* SID Version values for RD-N2 variants */
 #define RD_N2_CFG1_SID_VER_PART_NUM		0x07B6
+#define RD_N2_CFG3_SID_VER_PART_NUM		0x07F1
 
 /* SID Version values for RD-V2 */
 #define RD_V2_SID_VER_PART_NUM			0x07F2