xf86-video-r128 fails to build with --disable-dri

[Matt Turner]

It regressed between 6.10.2 and 6.11.0. See https://bugs.gentoo.org/666422

A quick glance indicates that it's due to 'widths' being defined only inside

#if defined(R128DRI) && defined(RENDER)
...
#endif

but being used unconditionally.

Thanks,
Matt