rust: regulator: remove Regulator<Dynamic>

rust: regulator: remove Regulator<Dynamic>

After some experimenting and further discussion, it is starting to look
like Regulator<Dynamic> might be a footgun. It turns out that one can
get the same behavior by correctly using just Regulator<Enabled> and
Regulator<Disabled>, so there is no need to directly expose the manual
refcounting ability of Regulator<Dynamic> to clients.

Remove it while we do not have any other users.

Suggested-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://patch.msgid.link/20250910-regulator-remove-dynamic-v3-1-07af4dfa97cc@collabora.com
Signed-off-by: Mark Brown <broonie@kernel.org>