MFC: r257862, r257863, r257864

r257862:

Use explicit long cast to avoid overflow in bitopts.

This was causing problems with the buddy allocator inside of
ofed.

r257863:

Fix for bad performance when mtu is increased.

Update the auto moderation behavior in the mlxen driver to match
the new LINUX OFED code.

r257864:

Do not use a sleep lock when protecting the driver flags.

This was causing a locking issue with lagg.

Approved by:	re
MFC r257749:
  Switch to using pkg(8) for the doc install in bsdinstall(8).
  This also bootstraps the system with pkg(8) for future use.

Approved by:	re (delphij)
PR:		183488
Sponsored by:	The FreeBSD Foundation