staging/rtl8187se: Fix compile warning 'is static but declared in .. which is not static'

When compiling this driver I get these compile warnings:

ieee80211.h:1227:2: warning: '______f' is static but declared in inline
function 'ieee80211_is_empty_essid' which is not static [enabled by
default]
ieee80211.h:1233:3: warning: '______f' is static but declared in inline
function 'ieee80211_is_empty_essid' which is not static [enabled by
default]
ieee80211.h:1248:2: warning: '______f' is static but declared in inline
function 'ieee80211_is_valid_mode' which is not static [enabled by
default]
ieee80211.h:1253:2: warning: '______f' is static but declared in inline
function 'ieee80211_is_valid_mode' which is not static [enabled by
default]
ieee80211.h:1258:2: warning: '______f' is static but declared in inline
function 'ieee80211_is_valid_mode' which is not static [enabled by
default]
ieee80211.h:1272:3: warning: '______f' is static but declared in inline
function 'ieee80211_get_hdrlen' which is not static [enabled by default]
ieee80211.h:1274:3: warning: '______f' is static but declared in inline
function 'ieee80211_get_hdrlen' which is not static [enabled by default]

These functions are declared as extern inline but not 'overloaded'
anywhere so we can declare them static inline and get rid of the
warnings.

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>