Indicate this uses dlmalloc.

Change-Id: Iaf5fd1f01487f4c63ccfef30d75a131485a3506c
diff --git a/BoardConfig.mk b/BoardConfig.mk
index 5c47707..3ae8850 100644
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -42,3 +42,5 @@
 include device/asus/grouper/BoardConfigCommon.mk
 
 TARGET_RECOVERY_FSTAB = device/asus/tilapia/fstab.grouper
+
+MALLOC_IMPL := dlmalloc