i965: Change the SF unit from state caching to state streaming.

i965: Change the SF unit from state caching to state streaming.

This is a 28.1% +/- 1.4% (n=10) performance improvement for the
hacked-up-for-cache-misses scissor-many (n=10), and no statistically
significant wall-time performance difference for the
hacked-up-for-cache-hits version (n=9, first outlier in each removed
since IPS was warming up.  User time increased by about 4.7%, but
kernel time decreased equivalently).