mlxbf-gige: Vitesse PHY stuck in a bad state during reboot test

[Asmaa Mnebhi]

SRU Justification:

[Impact]

During the QA reboot test, the BF3 Vitesse PHY gets stuck in a bad state, resulting in no ip provisioning. The only way to recover is to powercycle.
We found a software workaround to avoid getting in this state in the first place: disable the OOB port in the shutdown function.

[Fix]

* Prevent the PHY from entering this bad state by disabling the OOB port
  during shutdown.

[Test Case]

* do the reboot test (at least 2000 reboots): run 'reboot' from linux.
* Check that the oob_net0 interface is up and the ip is assigned.
* please note that if the the OOB doesn't get an ip, try reloading the driver (rmmod/modprobe). it that solves the issue, that would be a different bug. In the bug at stake, nothing recovers the OOB ip except power cycle.

[Regression Potential]

* Make sure the redfish DHCP is still working during the reboot test
* Make sure the OOB gets an ip

[Asmaa Mnebhi (asmaam)]

This SW WA didnt work so the HW team will have to review it.

[Asmaa Mnebhi (asmaam)]

Reopening this bug since we found a software workaround for it.