Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r263957:
Increase the number of TX DMA segments from 32 to 35. It turned
out 32 is not enough to support a full sized TSO packet.
While I'm here fix a long standing bug introduced in r169632 in
bce(4) where it didn't include L2 header length of TSO packet in
the maximum DMA segment size calculation.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

- Move ether_ifdetach() earlier and remove now-unneeded IN_DETACH flag.
- Expand locking in interrupt handler.

Reviewed by: yongari

Add a 'locked' variant of the foo_start() routine and call it directly
from interrupt handlers and watchdog routines instead of queueing a task
to call foo_start().

Reviewed by: yongari
MFC after: 1 month

Add support for Atheros AR8151/AR8152 PCIe gigabit/fast ethernet
controller. These controllers are known as L1D(AR8151) and
L2CB/B2(AR8152). This change adds supports for the following
controllers.
o AR8151 v1.0(L1D) gigabit ethernet controller
o AR8151 v2.0(L1D) gigabit ethernet controller
o AR8152 v1.1(L2CB) fast ethernet controller
o AR8152 v2.0(L2CB2) fast ethernet controller
These controllers have the same feature of AR8131/AR8132 and
support improved power saving control. The user visible change at
this moment is reduced jumbo frame size from 9KB to 6KB. Many
thanks to Atheros for continuing to support FreeBSD.

HW donated by: Atheros Communications, Inc.

Cache PCIY_PMG and PCIY_EXPRESS capability pointer to softc and use
it instead of calling pci_find_extcap().

Add alc(4), a driver for Atheros AR8131/AR8132 PCIe ethernet
controller. These controllers are also known as L1C(AR8131) and
L2C(AR8132) respectively. These controllers resembles the first
generation controller L1 but usage of different descriptor format
and new register mappings over L1 register space requires a new
driver. There are a couple of registers I still don't understand
but the driver seems to have no critical issues for performance and
stability. Currently alc(4) supports the following hardware
features.
o MSI
o TCP Segmentation offload
o Hardware VLAN tag insertion/stripping
o Tx/Rx interrupt moderation
o Hardware statistics counters(dev.alc.%d.stats)
o Jumbo frame
o WOL
AR8131/AR8132 also supports Tx checksum offloading but I disabled
it due to stability issues. I'm not sure this comes from broken
sample boards or hardware bugs. If you know your controller works
without problems you can still enable it. The controller has a
silicon bug for Rx checksum offloading, so the feature was not
implemented.
I'd like to say big thanks to Atheros. Atheros kindly sent sample
boards to me and answered several questions I had.

HW donated by: Atheros Communications, Inc.