Bullhead: Use 4 threads for dex2oat

Jank should be under control with CONFIG_HZ changes.

Bug: 26833007
Bug: 27689078
Change-Id: I54698739e33cd06bfe55080cecf38e22726e3735
diff --git a/device.mk b/device.mk
index 76f3b33..6a6ef59 100644
--- a/device.mk
+++ b/device.mk
@@ -413,7 +413,7 @@
 # limit dex2oat threads to improve thermals
 PRODUCT_PROPERTY_OVERRIDES += \
     dalvik.vm.boot-dex2oat-threads=4 \
-    dalvik.vm.dex2oat-threads=2 \
+    dalvik.vm.dex2oat-threads=4 \
     dalvik.vm.image-dex2oat-threads=4
 
 # Disable Camera TNR