freedreno/ir3: use uniform base

freedreno/ir3: use uniform base

When lowering from ubo, use the constant base field in the load_uniform
instruction for the constant part of the offset.  Doesn't change much
for constant indexing, but this will help for indirect indexing because
constant-folding can't completely clean up the result.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Eric Anholt <eric@anholt.net>