staging: r8188eu: remove ipx support from driver

The ipx.h header files are being removed from the kernel, and support
for them was long removed from the tree, so remove all references to it
in the r8188eu driver as well, to allow it to continue to build properly
in linux-next

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Phillip Potter <phil@philpotter.co.uk>
Link: https://lore.kernel.org/r/20210816073450.668993-2-gregkh@linuxfoundation.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>