i965/eu: Fix a bunch of compression control bugs in the generator.

Most of these were resetting quarter control to zero incorrectly even
though everything they needed to do was disable instruction
compression -- The brw_SAMPLE() case was doing the right thing but it
can be simplified slightly by using the new compression control
interface.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
2 files changed