This removes the support for disabling paged buffers.

USE_PAGED_BUFFERS has been the default and most tested mode
(since vendor-drop/v0.3.6.14.1 or earlier).

The vmware support was already non-functional, so there's no point
in keeping the detritus around.

The struct skb_frag_struct changed since Linux 5.4
commit 8842d285bafa9 ("net: Convert skb_frag_t to bio_vec") and
commit b8b576a16f79e ("net: Rename skb_frag_t size to bv_len")

The correct skb frag size accessors have been available since Linux 3.2
commit 9e903e085262 ("net: add skb frag size accessors")

Since Linux 5.0 the __ETHTOOL_LINK_MODE_LAST macro has been replaced
with __ETHTOOL_LINK_MODE_MASK_NBITS.

Since Linux 5.0 the __ETHTOOL_LINK_MODE_LAST macro is no longer available.
commit e728fdf06289 ("net: phy: improve definition of __ETHTOOL_LINK_MODE_MASK_NBITS")
replaced it with __ETHTOOL_LINK_MODE_MASK_NBITS.

In v0.3.6.17.2 the vendor driver replaced __ETHTOOL_LINK_MODE_LAST+1
with 0xFFFFFFFF. This reverts that, because we want to use the proper
solution that upstream drivers use, namely
__ETHTOOL_LINK_MODE_MASK_NBITS.

This change provides minimal support for the SANLink3 T1 Thunderbolt3
NBase-T adapter (https://www.promise.com/Products/SANLink/SANLink3-T1),
which has the TN4025 with an AQR105 inside it.

The interface comes up, does negotiation, brings up link at 10 Gbit/s
and achieves OK throughput (8 Gbit/s).  The modest throughput might be
related to errors that are periodically logged by the driver:

  [462738.525551] rxd_err = 0x4
  [462738.670364] rxd_err = 0x4
  ...

I didn't have any NBase-T switches offhand to test 2.5G or 5G rates,
so I don't know if that works.

This change didn't work earlier on the 0.3.6.15 driver, so I suspect
it requires the 2.b.e2 AQR105 firmware mentioned in release_notes.

This driver was downloaded from:
http://www.tehutinetworks.net/?t=drivers&L1=8&L2=12&L3=26&L4=0&L5=0&L6=0&L7=0&f=tn40xx-0.3.6.17.2.tgz

The source code was extracted, but not modified.

Thanks to Jean-Christophe Heger for contributing DKMS support.

Prepare for 001 release:
* briefly describe dkms
* change version for release
* change clone url to point to release repo

move branch descriptions and vendor diffs to docs/

Removes the redundant STRING_FMT macro that vendor added in v0.3.6.16

replace DBG(...) with pr_debug(...)
replace MSG(...) with pr_info(...)
replace ERR(...) with pr_err(...)
and
remove unused DBG, MSG, ERR macros

The cleanup step for removing redundant returns at the end of void
functions (added in commit 49c0bf4a) was flawed. Redundant returns have
a space (ie. 'return ;'), so adjust the regex to match that.

upstream fixed this variable name in 0.3.16.15 and this backports the
fix to make diffs between cleanup branches smaller.