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.

MFC r246341:
Rework jumbo frame handling. QAC confirmed that the controller
requires 8 bytes alignment on RX buffer. Given that non-jumbo
frame works on any alignments I guess this DMA limitation for RX
buffer could be jumbo frame specific one. Also I'm not sure
whether this DMA limitation is related with 64bit DMA. Previously
age(4) disabled 64bit DMA addressing due to silent data corruption.
So we may need more testing on re-enabling 64bit DMA in future.

While I'm here, change mbuf chaining algorithm to use fixed sized
buffer and force software checksum if controller reports length
error. According to QAC, RFD is not updated at all for jumbo frame
so it works just like alc(4) controllers. This change also added
alignment fixup for strict alignment architectures. Because I'm
not aware of any non-x86 machines that use age(4) controllers it's
just for completeness at this moment.

Wit this change, jumbo frame should work with age(4).

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

Approved by: re (implicit)

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

Remove unused age_txdq

Add age(4), a driver for Attansic/Atheros L1 gigabit ethernet
controller. L1 has several threshold/timer registers and they
seem to require careful tuned parameters to get best
performance. Datasheet for L1 is not available to open source
driver writers so age(4) focus on stability and correctness of
basic Tx/Rx operation. ATM the performance of age(4) is far from
optimal which in turn means there are mis-programmed registers or
incorrectly configured registers.
Currently age(4) supports all known hardware assistance including
- MSI support.
- TCP Segmentation Offload.
- Hardware VLAN tag insertion/stripping.
- TCP/UDP checksum offload.
- Interrupt moderation.
- Hardware statistics counter support.
- Jumbo frame support.
- WOL support.

L1 gigabit ethernet controller is mainly found on ASUS
motherboards. Note, it seems that there are other variants of
hardware as known as L2(Fast ethernet) and newer gigabit ethernet
(AR81xx) from Atheros. These are not supported by age(4) and
requires a seperate driver. Big thanks to all people who reported
feedback or tested patches.

Tested by: kevlo, bsam, Francois Ranchin < fyr AT fyrou DOT net >
Thomas Nystroem < thn AT saeab DOT se >
Roman Pogosyan < asternetadmin AT gmail DOT com >
Derek Tattersal < dlt AT mebtel DOT net >
Oliver Seitz < karlkiste AT yahoo DOT com >