Staging: rtl8192u: fix checkpatch.pl error

This patch fixes the checkpatch.pl script error:
ERROR: do not use C99 // comments
+static long ieee80211_translate_todbm(u8 signal_strength_index)// 0-100
index.
Signed-off-by: Teodora Baluta <teobaluta@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/ieee80211/ieee80211_rx.c

@@ -2166,7 +2166,8 @@ static inline u8 ieee80211_SignalStrengthTranslate(
 	return RetSS;
 }
 
-static long ieee80211_translate_todbm(u8 signal_strength_index)// 0-100 index.
+/* 0-100 index */
+static long ieee80211_translate_todbm(u8 signal_strength_index)
 {
 	long	signal_power; // in dBm.