i965: Replace 8-wide and 16-wide with SIMD8 and SIMD16.

i965: Replace 8-wide and 16-wide with SIMD8 and SIMD16.

Those are the terms used in the docs, and think "n-wide" was something I
just happened to say.  Note that shader-db needs updating for the
INTEL_DEBUG=fs parsing.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>