Retire the default_smbusespi uart-service constructor

[dymk]

Final step of the DSP0253 serial-framing unification: the SMBus/eSPI uart-service convenience path has no remaining callers, so this removes it.

Context

This completes the cascade that moved the EC ↔ SP UART relay off the hand-rolled SMBus/eSPI framing and onto DSP0253 serial (MctpSerialMedium):

• OpenDevicePartnership/odp-platform-common#132 — ec-test-lib → DSP0253
• Switch all platforms to the MctpSerial uart-service odp-embedded-controller#36 — all 5 EC platforms → default_mctp_serial
• uart-service: add default_mctp_serial constructor #906 — added the default_mctp_serial constructor

With every consumer now on MctpSerialService::default_mctp_serial, default_smbusespi and the DefaultService alias are dead code.

Change

uart-service/src/lib.rs only:

• Remove the DefaultService<R> alias and its default_smbusespi constructor.
• Drop the now-unused SmbusEspiMedium / SmbusEspiReplyContext imports.
• Update the module doc to point at MctpSerialService.

SmbusEspiMedium itself is untouched — it stays in mctp-rs and remains in use by espi-service and the relay layer. Only the uart-service convenience wrapper is retired; the generic Service<R, M> can still be built with any medium via Service::new.

Verification

• cargo build / cargo clippy --all-targets — clean
• cargo test — 245 passed / 5 ignored
• cargo deny check advisories + cargo vet — pass
• Confirmed zero remaining default_smbusespi / DefaultService references (incl. examples)

Assisted-by: GitHub Copilot:claude-opus-4.8

[Copilot]

Pull request overview

This PR removes the now-dead DefaultService<R> alias and its default_smbusespi() constructor from uart-service, completing the migration to DSP0253 serial framing via MctpSerialService::default_mctp_serial(). It also drops the corresponding unused SmbusEspiMedium/SmbusEspiReplyContext imports and updates the crate-level docs to steer users to the serial baseline. The generic Service<R, M> remains available for constructing a UART relay with any mctp_rs::MctpMedium, so this change strictly retires the SMBus/eSPI convenience wrapper rather than the underlying medium support.

Changes:

• Remove DefaultService<R> and default_smbusespi() from the public API.
• Remove now-unused mctp_rs::smbus_espi::{SmbusEspiMedium, SmbusEspiReplyContext} imports.
• Update module docs to reference MctpSerialService as the baseline constructor/alias.

Step-by-step review guide

1. Crate-level guidance update

   • The top-level docs now direct users to MctpSerialService (DSP0253 serial) and to Service::new for other media.
   • This is the primary “migration hint” surface for users reading rustdoc; worth confirming it matches the intended supported path.

2. Public API surface reduction

   • The DefaultService<R> = Service<R, SmbusEspiMedium> alias and default_smbusespi() constructor are removed.
   • This is an intentional API removal; within this repo, there are no remaining references to DefaultService or default_smbusespi (confirmed by search).

3. Serial baseline remains

   • MctpSerialService<R> and default_mctp_serial() remain as the canonical convenience constructor, with per-response destination EID still overridden in process_response.

Potential issues

No issues found.