freedreno/batch: fix dependency loop detection

freedreno/batch: fix dependency loop detection

We can have a scenario like:

  A -> B
  A -> C -> B

When adding the A->C dependency, it doesn't really matter that C depends
on something that A depends on, that isn't a necessary condition for a
dependency loop.

Instead what we want to know is that nothing C depends on, directly or
indirectly, depends on A.  We can detect this by recursively OR'ing the
dependents_mask of C and all it's dependencies.

Signed-off-by: Rob Clark <robdclark@chromium.org>