MFC r313497: ixl(4): Update to 1.7.12-k.

MFC r313497: ixl(4): Update to 1.7.12-k.

Refresh upstream driver before impending conversion to iflib.

Major new features:

- Support for Fortville-based 25G adapters
- Support for I2C reads/writes

(To prevent getting or sending corrupt data, you should set
dev.ixl.0.debug.disable_fw_link_management=1 when using I2C
[this will disable link!], then set it to 0 when done. The driver implements
the SIOCGI2C ioctl, so ifconfig -v works for reading I2C data,
but there are read_i2c and write_i2c sysctls under the .debug sysctl tree
[the latter being useful for upper page support in QSFP+]).

- Addition of an iWARP client interface (so the future iWARP driver for
  X722 devices can communicate with the base driver).
    - Add "options IXL_IW" to kernel config to enable this option.

Sponsored by:	Intel Corporation