staging: brcm80211: removed counter related struct wl_cnt

Code cleanup. Struct wl_cnt contains all sorts of counters, but either these
were written and never read, or set to zero at initialization but never
updated. Therefore the struct and any code accessing the struct has been
removed.

Cc: devel@linuxdriverproject.org
Cc: linux-wireless@vger.kernel.org
Reviewed-by: Henry Ptasinski <henryp@broadcom.com>
Reviewed-by: Brett Rudley <brudley@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>