staging: rtl8188eu: Change type of rtw_get_sec_ie()

Change return type of function rtw_get_sec_ie from int to void and
remove its return statement as the return value is never stored, checked
or otherwise used.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>