Add proper checks for PAN & BNEP in BD stack

This patch fixes issues for PAN & BNEP in BD stack identified
by static analysis tool.

Change-Id: I29417dae982abb5cef11379f8d03baad11ffde8b
diff --git a/btif/include/btif_pan_internal.h b/btif/include/btif_pan_internal.h
index 64bab99..fad5577 100644
--- a/btif/include/btif_pan_internal.h
+++ b/btif/include/btif_pan_internal.h
@@ -38,6 +38,7 @@
 #define PANU_SERVICE_NAME "Android Network User"
 #define TAP_IF_NAME "bt-pan"
 #define ETH_ADDR_LEN        6
+#define TAP_MAX_PKT_WRITE_LEN 2000
 #ifndef PAN_SECURITY
 #define PAN_SECURITY (BTM_SEC_IN_AUTHENTICATE | BTM_SEC_OUT_AUTHENTICATE | BTM_SEC_IN_ENCRYPT | BTM_SEC_OUT_ENCRYPT)
 #endif