samples: rust: convert PCI rust sample driver to use try_access_with()

This method limits the scope of the revocable guard and is considered
safer to use for most cases, so let's showcase it here.

Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/r/20250411-try_with-v4-2-f470ac79e2e2@nvidia.com


Signed-off-by: Danilo Krummrich <dakr@kernel.org>