qcacld-3.0: Make hdd_display_stats_help() static
Currently hdd_display_stats_help() is a public function exported by
wlan_hdd_wext.h. But this function is only used internally within
wlan_hdd_wext.c, so remove the public prototype and instead make the
function static.
Change-Id: Iaed10720f0f325794481bbb7ad9f743deb6b7b15
CRs-Fixed: 2227013