staging: rtl8192u: Move export_symbol below its function

Move export_symbol below its function in ieee80211/dot11d.c

Fix checkpatch.pl warning:
WARNING: EXPORT_SYMBOL(foo); should immediately follow its function/variable

Signed-off-by: Ana Rey <anarey@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>