ixgbe: Support external GBE SerDes PHY BCM54616s

The Broadcom PHY is used in switches, so add the ID, and hook it up.

This upstreams the Linux kernel patch from the network operating system
SONiC from February 2020 [1].

[1]: https://github.com/Azure/sonic-linux-kernel/pull/122



Signed-off-by: Jostar Yang <jostar_yang@accton.com>
Signed-off-by: Guohan Lu <lguohan@gmail.com>
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Tested-by: Tony Brelinski <tonyx.brelinski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>