default to 3.18.x as long the qemu-arm problem is unresolved

target/config/Config.in.kernelversion.choice

@@ -4,6 +4,7 @@
 choice
 prompt "Kernel Version"
 depends on ADK_TARGET_KERNEL_CUSTOMISING
+default ADK_KERNEL_VERSION_3_18_6
 
 config ADK_KERNEL_VERSION_3_19_0
 	bool "3.19"