net: phy: broadcom: Set proper 1000BaseX/SGMII interface mode for BCM54616S

[ Upstream commit 3afd0218

 ]

The default configuration for the BCM54616S PHY may not match the desired
mode when using 1000BaseX or SGMII interface modes, such as when it is on
an SFP module. Add code to explicitly set the correct mode using
programming sequences provided by Bel-Fuse:

https://www.belfuse.com/resources/datasheets/powersolutions/ds-bps-sfp-1gbt-05-series.pdf
https://www.belfuse.com/resources/datasheets/powersolutions/ds-bps-sfp-1gbt-06-series.pdf

Signed-off-by: Robert Hancock <robert.hancock@calian.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>