igc(4): Fix attach for I226-K and LMVP devices

Summary:
The device IDs for these were in the driver's list of PCI ids to attach
to, but igc_set_mac_type() had never been setup to set the correct mac
type for these devices. Fix this by adding these IDs to the switch block
in order for them to be recognized by the driver instead of returning an
error.

This fixes the igc(4) attach for the I226-K LOM on the ASRock Z790
PG-ITX/TB4 motherboard, allowing it to be recognized and used.

Signed-off-by: Eric Joyner <erj@FreeBSD.org>

Reviewed by: kbowling@
MFC after: 3 days
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D49147