staging: rtl8192u: make in ieee80211/ieee80211_tx.c some local functions static

Make some local functions (ieee80211_qurey_ShortPreambleMode and
ieee80211_query_HTCapShortGI) static and fix coding style in these
function declarations when It is necessary.

Fix the following sparse warnings in ieee80211/ieee80211_tx.c

drivers/staging/rtl8192u/ieee80211/ieee80211_tx.c:381:6: warning: symbol 'ieee80211_qurey_ShortPreambleMode' was not declared. Should it be static?
drivers/staging/rtl8192u/ieee80211/ieee80211_tx.c:395:1: warning: symbol 'ieee80211_query_HTCapShortGI' was not declared. Should it be static?

Signed-off-by: Ana Rey <anarey@gmail.com>
Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>