platform: msm8994: Set flag for armv8 core

Add macro to idenify the armv8 core.

Change-Id: Ib4cf1abbc8bd98767d20d8ed2cac94bfbda8f310
diff --git a/platform/msm8994/rules.mk b/platform/msm8994/rules.mk
index 23fb133..a9fd66f 100644
--- a/platform/msm8994/rules.mk
+++ b/platform/msm8994/rules.mk
@@ -5,6 +5,7 @@
 CPU     := generic
 
 DEFINES += ARM_CPU_CORE_KRAIT
+DEFINES += ARM_CORE_V8
 
 MMC_SLOT         := 1