plat/arm/css: Add SID registers for SGx platforms

Some of the SGx platforms use System Identification (SID) registers
for platform identification. Add support for these registers in css.

Change-Id: If00b18744a31ff2cf14338f18c8c680eb69c9027
Signed-off-by: Chandni Cherukuri <chandni.cherukuri@arm.com>

include/plat/arm/css/common/css_def.h

@@ -26,6 +26,11 @@
 #define SSC_REG_BASE			0x2a420000
 #define SSC_GPRETN			(SSC_REG_BASE + 0x030)
 
+/* System ID Registers Unit */
+#define SID_REG_BASE			0x2a4a0000
+#define SID_SYSTEM_ID_OFFSET		0x40
+#define SID_SYSTEM_CFG_OFFSET		0x70
+
 /* The slave_bootsecure controls access to GPU, DMC and CS. */
 #define CSS_NIC400_SLAVE_BOOTSECURE	8
 
@@ -123,6 +128,8 @@
 #define SSC_VERSION_DESIGNER_ID_MASK		0xff
 #define SSC_VERSION_PART_NUM_MASK		0xfff
 
+#define SID_SYSTEM_ID_PART_NUM_MASK		0xfff
+
 /* SSC debug configuration registers */
 #define SSC_DBGCFG_SET		0x14
 #define SSC_DBGCFG_CLR		0x18