This is a port of Danylo's eca4a6548d
which fixed the hang on i965. It fixes GPU hangs in his new Piglit
test, arb_blend_func_extended-dual-src-blending-discard-without-src1.
I avoided my own review feedback here, and decided to simply adjust
3DSTATE_PS_BLEND rather than BLEND_STATE_ENTRY[0]. It has never been
clear to me which the hardware uses in every case. However, whacking
the enable in 3DSTATE_PS_BLEND seems to be sufficient to fix the hang,
and that packet is already dynamic, so it's easy to handle. I'd rather
avoid making BLEND_STATE_ENTRY[0] dynamic unless I have to.
5ff5d0a895