qcacld-3.0: Fix mib stats feature compile error on perf image

With perf kernel config file, it usually will not
set CONFIG_DEBUG_FS=y, which will cause implicit
declaration of function 'hdd_debugfs_process_mib_stats'
such compile error. And MIB STATS feature also depend
on debug fs, so enable it as long as CONFIG_DEBUG_FS=y

Change-Id: Ice1ddce07eb5eb251e766d3952ca15b00321b3b2
CRs-Fixed: 2829413

configs/qca6390_defconfig

@@ -637,7 +637,6 @@ CONFIG_FEATURE_WLAN_LPHB := y
 CONFIG_QCA_SUPPORT_TX_THROTTLE := y
 CONFIG_WMI_INTERFACE_EVENT_LOGGING := y
 CONFIG_WLAN_FEATURE_LINK_LAYER_STATS := y
-CONFIG_WLAN_FEATURE_MIB_STATS := y
 CONFIG_FEATURE_WLAN_EXTSCAN := n
 CONFIG_WMI_BCN_OFFLOAD := y
 CONFIG_160MHZ_SUPPORT := y
@@ -656,6 +655,10 @@ CONFIG_FEATURE_MONITOR_MODE_SUPPORT := y
 CONFIG_WLAN_ALLOCATE_GLOBAL_BUFFERS_DYNAMICALLY := n
 CONFIG_WLAN_FEATURE_TWT := y
 
+ifeq ($(CONFIG_WLAN_DEBUGFS), y)
+       CONFIG_WLAN_FEATURE_MIB_STATS := y
+endif
+
 ifeq (y,$(findstring y,$(CONFIG_LITHIUM) $(CONFIG_ICNSS)))
 CONFIG_WLAN_FEATURE_BMI := n
 else