i965: Update compute workgroup size limit calculation for SIMD32.
i965: Update compute workgroup size limit calculation for SIMD32.

This should have the side effect of enabling the ARB_compute_shader
extension on Gen8+ hardware and all Gen7 platforms that didn't
previously expose it (VLV and IVB GT1) due to the number of hardware
threads per subslice being insufficient in SIMD16 mode.

v2: Bump workgroup size limit for GLES too (Jordan).

Reviewed-by: Jason Ekstrand <68c46a606457643eab92053c1c05574abb26f861@jlekstrand.net>
Reviewed-by: Jordan Justen <a79006884ba9cf5f4f7fcbb92a15b208780d8c97@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler