TF-A: Add GICv4 extension for GIC driver

This patch adds support for GICv4 extension.
New `GIC_ENABLE_V4_EXTN` option passed to gicv3.mk makefile
was added, and enables GICv4 related changes when set to 1.
This option defaults to 0.

Change-Id: I30ebe1b7a98d3a54863900f37eda4589c707a288
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
diff --git a/include/drivers/arm/gicv3.h b/include/drivers/arm/gicv3.h
index c29896b..03596b9 100644
--- a/include/drivers/arm/gicv3.h
+++ b/include/drivers/arm/gicv3.h
@@ -151,9 +151,13 @@
 #define	TYPER_ESPI_RANGE	U(TYPER_ESPI_MASK << TYPER_ESPI_SHIFT)
 
 /*******************************************************************************
- * GICv3 and 3.1 Redistributor interface registers & constants
+ * Common GIC Redistributor interface registers & constants
  ******************************************************************************/
+#if GIC_ENABLE_V4_EXTN
+#define GICR_PCPUBASE_SHIFT	0x12
+#else
 #define GICR_PCPUBASE_SHIFT	0x11
+#endif
 #define GICR_SGIBASE_OFFSET	U(65536)	/* 64 KB */
 #define GICR_CTLR		U(0x0)
 #define GICR_IIDR		U(0x04)