freedreno/ir3: intra-block scheduling

freedreno/ir3: intra-block scheduling

Because of loops, we can't schedule all of a block's predecessors first.
Instead just assume that the result consumed in a block was written far
enough away in all paths into a block.  And do an intra-block scheduling
pass to figure out if there are any cases where we need to insert extra
nop's.  This works out better than always assuming the worst case (ie.
that a value live into a block was written in the last instruction in
the predecessor block).

Signed-off-by: Rob Clark <robdclark@gmail.com>