sfxge(4): use transceiver ID when reading info

In efx_mcdi_phy_module_get_info() probe the
transceiver identification byte rather than assume
the module matches the fixed port type. This
supports scenarios such as a SFP mounted in a QSFP
port via a QSA module.

Submitted by: Richard Houldsworth <rhouldsworth at solarflare.com>
Sponsored by: Solarflare Communications, Inc.
Differential Revision: https://reviews.freebsd.org/D18282