Revert "Delete unused import statement for Executorch TOSA dialect (#… (pytorch#12301)

…12269)"

This reverts commit 9327708.

### Summary
[PLEASE REMOVE] See [CONTRIBUTING.md's Pull
Requests](https://github.com/pytorch/executorch/blob/main/CONTRIBUTING.md#pull-requests)
for ExecuTorch PR guidelines.

[PLEASE REMOVE] If this PR closes an issue, please add a `Fixes
#<issue-id>` line.

[PLEASE REMOVE] If this PR introduces a fix or feature that should be
the upcoming release notes, please add a "Release notes: <area>" label.
For a list of available release notes labels, check out
[CONTRIBUTING.md's Pull
Requests](https://github.com/pytorch/executorch/blob/main/CONTRIBUTING.md#pull-requests).

### Test plan
[PLEASE REMOVE] How did you test this PR? Please write down any manual
commands you used and note down tests that you have written if
applicable.

Author: psiddh

backends/arm/_passes/arm_pass_manager.py

@@ -6,6 +6,8 @@
 # LICENSE file in the root directory of this source tree.
 
 # pyre-unsafe
+
+import executorch.backends.arm.tosa.dialect  # noqa: unused
 from executorch.backends.arm._passes import (
     AddBiasPass,
     AnnotateChannelsLastDimOrder,