Revert "ixgbe: Manual AN-37 for troublesome link partners for X550 SFI"

Revert "ixgbe: Manual AN-37 for troublesome link partners for X550 SFI"

This reverts commit 565736048bd5f9888990569993c6b6bfdf6dcb6d.

According to the commit, it implements a manual AN-37 for some
"troublesome" Juniper MX5 switches. This appears to be a workaround for a
particular switch.

It has been reported that this causes a severe breakage for other switches,
including a Cisco 3560CX-12PD-S.

The code appears to be a workaround for a specific switch which fails to
link in SFI mode. It expects to see AN-37 auto negotiation in order to
link. The Cisco switch is not expecting AN-37 auto negotiation. When the
device starts the manual AN-37, the Cisco switch decides that the port is
confused and stops attempting to link with it. This persists until a power
cycle. A simple driver unload and reload does not resolve the issue, even
if loading with a version of the driver which lacks this workaround.

The authors of the workaround commit have not responded with
clarifications, and the result of the workaround is complete failure to
connect with other switches.

This appears to be a case where the driver can either "correctly" link with
the Juniper MX5 switch, at the cost of bricking the link with the Cisco
switch, or it can behave properly for the Cisco switch, but fail to link
with the Junipir MX5 switch. I do not know enough about the standards
involved to clearly determine whether either switch is at fault or behaving
incorrectly. Nor do I know whether there exists some alternative fix which
corrects behavior with both switches.

Revert the workaround for the Juniper switch.

Fixes: 565736048bd5 ("ixgbe: Manual AN-37 for troublesome link partners for X550 SFI")
Link: https://lore.kernel.org/netdev/cbe874db-9ac9-42b8-afa0-88ea910e1e99@intel.com/T/
Link: https://forum.proxmox.com/threads/intel-x553-sfp-ixgbe-no-go-on-pve8.135129/#post-612291
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Cc: Jeff Daly <jeffd@silicom-usa.com>
Cc: kernel.org-fo5k2w@ycharbi.fr
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240520-net-2024-05-20-revert-silicom-switch-workaround-v1-1-50f80f261c94@intel.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>