freedreno/ir3: relative dst

freedreno/ir3: relative dst

To simplify RA, assign arrays that are written to first.  Since enough
dependency information is in the graph to preserve order of reads and
writes of array, so all SSA names for the array collapse into one, just
assign the entire thing by array-id.

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