i965: don't include compute resources in "Combined" limits

i965: don't include compute resources in "Combined" limits

The combined limits should only include shader stages that can be active
at the same time.  We don't need to include compute.

See also cff290df4c09547cd2cb3b129ec59bdebdadba90 for st/mesa.

Unbreaks i965 from assert failing on driver load since Marek's
45f87a48f94148b484961f18a4f1ccf86f066b1c, which dropped the core
Mesa capabilities before adjusting driver limits down to match.