staging: rtl8188eu: remove rtw_ioctl_rtl.h

The header rtw_ioctl_rtl.h is not used anywhere.
Running 'grep -r rtw_ioctl_rtl *' from kernel root
directory returns nothing, remove the file.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>