aco/lower_branches: keep blocks with multiple logical successors

It might be the case that both the branch and exec mask write in a
divergent branch block are removed. try_remove_simple_block() might then
try to remove it, but fail because it has multiple logical successors.
Instead, just skip these blocks.

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Backport-to: 25.1
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35202>

src/amd/compiler/aco_lower_branches.cpp

@@ -553,7 +553,7 @@ lower_branches(Program* program)
       if (block.kind & block_kind_break)
          try_merge_break_with_continue(ctx, block);
 
-      if (block.linear_succs.size() == 1)
+      if (block.linear_succs.size() == 1 && block.logical_succs.size() <= 1)
          try_remove_simple_block(ctx, block);
    }