staging: rtl8723au: Remove buggy function _rtw_report_sec_ie()

This function was extremely buggy calling kmalloc(GFP_KERNEL) while
holding a spin lock and then potentially overflowing the buffer it had
allocated.

Since the generated output wasn't used for anything, simply rip the
whole thing out.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>