staging: rtl8188eu: clean up indent style issue

Replace spaces with tab to clear checkpatch error.

ERROR: code indent should use tabs where possible
Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20200929062847.23985-8-straube.linux@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>