allwinner: Introduce names for SoC IDs

We will soon make more use of the Allwinner SoC ID, to differentiate the
platform setup.
Introduce definitions to avoid dealing with magic numbers and make the
code more readable.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/plat/allwinner/common/include/sunxi_def.h b/plat/allwinner/common/include/sunxi_def.h
index e68fbe4..da87b23 100644
--- a/plat/allwinner/common/include/sunxi_def.h
+++ b/plat/allwinner/common/include/sunxi_def.h
@@ -14,4 +14,8 @@
 #define SUNXI_UART0_BAUDRATE		115200
 #define SUNXI_UART0_CLK_IN_HZ		SUNXI_OSC24M_CLK_IN_HZ
 
+#define SUNXI_SOC_A64			0x1689
+#define SUNXI_SOC_H5			0x1718
+#define SUNXI_SOC_H6			0x1728
+
 #endif /* __SUNXI_DEF_H__ */
diff --git a/plat/allwinner/common/sunxi_bl31_setup.c b/plat/allwinner/common/sunxi_bl31_setup.c
index 7e11cec..b56b9ee 100644
--- a/plat/allwinner/common/sunxi_bl31_setup.c
+++ b/plat/allwinner/common/sunxi_bl31_setup.c
@@ -68,13 +68,13 @@
 	uint16_t soc_id = sunxi_read_soc_id();
 
 	switch (soc_id) {
-	case 0x1689:
+	case SUNXI_SOC_A64:
 		soc_name = "A64/H64/R18";
 		break;
-	case 0x1718:
+	case SUNXI_SOC_H5:
 		soc_name = "H5";
 		break;
-	case 0x1728:
+	case SUNXI_SOC_H6:
 		soc_name = "H6";
 		break;
 	default: