BT: Disable BT Dial up Networking

- Disable DUN.
- Use feature flag to compile dun modules.

CRs-fixed: 2610157
Change-Id: I832ab5abd33b11d2c9c0bdbe7c7a8ad1a292d9cd
diff --git a/bt-commonsys-intf-legacy-aosp-board.mk b/bt-commonsys-intf-legacy-aosp-board.mk
index f54ab6c..ddd2607 100644
--- a/bt-commonsys-intf-legacy-aosp-board.mk
+++ b/bt-commonsys-intf-legacy-aosp-board.mk
@@ -8,3 +8,4 @@
 TARGET_USE_QTI_BT_CONFIGSTORE := false
 TARGET_USE_QTI_BT_SAR := false
 TARGET_USE_QTI_VND_FWK_DETECT := false
+TARGET_USE_BT_DUN := false