sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

igc: Remove redundant IFCAP_VLAN_HWTAGGING check

Match igb(4) as in f7926a6d0c10. From Vincenzo, this check is redundant
to setup providing us an IGC_RXD_STAT_VP bit and would make for an
unexpected condition if IFCAP_VLAN_HWTAGGING were not set but the tag
was stripped, which would be passed up the stack breaking isolation.

PR: 260068
Approved by: vmaffione
MFC after: 1 month

net: iflib: fix vlan processing in the drivers

The logic that sets iri_vtag and M_VLANTAG does not handle the
case where the 802.11q VLAN tag is 0. Fix this issue across
the iflib drivers. While there, also improve and align the
VLAN tag check extraction, by moving it outside the RX descriptor
loop, eliminating a local variable and additional checks.

PR: 260068
Reviewed by: kbowling, gallatin
Reported by: erj
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D33156

igc: sync igc_txrx with igb(4)

Reviewed by: grehan
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D31227

igc(4): Introduce new driver for the Intel I225 Ethernet controller.

This controller supports 2.5G/1G/100MB/10MB speeds, and allows
tx/rx checksum offload, TSO, LRO, and multi-queue operation.

The driver was derived from code contributed by Intel, and modified
by Netgate to fit into the iflib framework.

Thanks to Mike Karels for testing and feedback on the driver.

Reviewed by: bcr (manpages), kbowling, scottl, erj
MFC after: 1 month
Relnotes: yes
Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D30668