staging: brcm80211: fix for 'Short CCK' log spam

Larry Finger reported this issue. Under certain conditions the log
file would be spammed with 'Short CCK' messages. Since this does
not indicate an error condition, the log message was simply
deleted. Also, the RX_FLAG_SHORTPRE flag in rx_status->flag, on
CCK reception, is now only set on short preamble reception (it used
to be set both CCK short and long preambles).

Signed-off-by: Roland Vossen <rvossen@broadcom.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>