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 253048,253423,253449,253653,253774,253785:
- Allow mlx4 devices to switch between Ethernet and Infiniband:
- Fix sysfs attribute handling by using sysctl_handle_string() and
properly handling trailing newlines in attribute values.
- Remove check forbidding requests that would result in one port being
set to Ethernet and the subsequent port being set to IB.
- Avoid trashing IP fragments by correctly managing hardware checksumming.
- Fix panics when downing or unloading the mlx4 driver.

PR: kern/179999, kern/174213, kern/180430, kern/180791

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

Approved by: re (implicit)

- Implement wake-on-lan support in mlxen.

- Merge in OFED 1.5.3 from projects/ofed/head