qcacld-3.0: Modify Kbuild to add new beacon header file

In wmi new file, wmi_unified_bcn_api.c is added.
Add this file in Kbuild.

Change-Id: I4fdbf041b53b5f1606d324714f01088742a9307f
CRs-Fixed: 2366772
diff --git a/configs/default_defconfig b/configs/default_defconfig
index 433b09c..7000c21 100644
--- a/configs/default_defconfig
+++ b/configs/default_defconfig
@@ -604,6 +604,7 @@
 CONFIG_WMI_INTERFACE_EVENT_LOGGING := y
 CONFIG_WLAN_FEATURE_LINK_LAYER_STATS := y
 CONFIG_FEATURE_WLAN_EXTSCAN := y
+CONFIG_WMI_BCN_OFFLOAD := y
 CONFIG_160MHZ_SUPPORT := y
 CONFIG_MCL := y
 CONFIG_MCL_REGDB := y