rust: driver: update module documentation for GAT-based Data type

rust: driver: update module documentation for GAT-based Data type

Now that all bus driver traits use type Data<'bound>: 'bound, update the
illustrative driver trait in the module documentation to reflect the GAT
pattern and lifetime-parameterized callbacks.

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260525202921.124698-18-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>