zfs: Revert "Fix data race between zil_commit() and zil_suspend()"

This reverts commit 4c856fb333ac57d9b4a6ddd44407fd022a702f00.

To quote a pending upstream PR:
This reverts commit 4c856fb to resolve a newly introduced deadlock which
in practice is more disruptive that the issue this commit intended to
address.

Causes deadlocks described in https://github.com/openzfs/zfs/issues/14775

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