Set default kernel path to third_party.

Change-Id: I916761a2d58baf969c4abc48ad6289a407878987
diff --git a/Makefile b/Makefile
index 93804f6..18f01a6 100644
--- a/Makefile
+++ b/Makefile
@@ -29,7 +29,7 @@
 
 else
 
-KERNEL_PATH ?= $(HAFNIUM_PATH)/../linux
+KERNEL_PATH ?= $(HAFNIUM_PATH)/third_party/linux
 ARCH ?= arm64
 CROSS_COMPILE ?= aarch64-linux-gnu-