i965/fs: Don't double-emit SEND dependency workarounds at control flow.

i965/fs: Don't double-emit SEND dependency workarounds at control flow.

We weren't setting needs_dep[i] in the loops, so we'd continue on to
potentially add the same workaround MOVs to the later basic block
boundaries, too.  We can either set needs_dep[i] to exit through the
normal path, or we can just return since we know we're done.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>