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@
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D49147

(cherry picked from commit 7ee310c80ea7b336972f53cc48b8c3d03029941e)