vc4: Redefine VPM writes as a (destination) QIR register file.

This will let me coalesce the VPM writes into the instructions generating
the values.
vc4: Coalesce MOVs into VPM with the instructions generating the values.

total instructions in shared programs: 41168 -> 40976 (-0.47%)
instructions in affected programs:     18156 -> 17964 (-1.06%)
i965/fs: Add missing const qualifier.
freedreno/ir3: hack for standalone compiler

Standalone compiler doesn't have screen or context.  We need to come up
with a better way to control the target arch (ie. something that we can
control from cmdline w/ standalone compiler) but for now this hack keeps
it from segfault'ing.

Signed-off-by: Rob Clark <robclark@freedesktop.org>
freedreno/ir3: trans_kill cleanup

trans_kill() only handles the single opcode.  Drop the remnant of a time
when both KILL and KILL_IF were handled by the same fxn.

Signed-off-by: Rob Clark <robclark@freedesktop.org>
freedreno: update generated headers
freedreno/a4xx: alpha-test

Signed-off-by: Rob Clark <robclark@freedesktop.org>
freedreno/a4xx: blend-color

Signed-off-by: Rob Clark <robclark@freedesktop.org>