net: phy: Add AFE settings to the Broadcom Cygnus phy

Added the AFE (Analog Front End) settings for stability to the
Broadcom Cygnus phy. This improves the time take to perform
auto negotiation.

Signed-off-by: Arun Parameswaran <arun.parameswaran@broadcom.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>