net: sfp: add support for multigig RollBall transceivers

This adds support for multigig copper SFP modules from RollBall/Hilink.
These modules have a specific way to access clause 45 registers of the
internal PHY.

We also need to wait at least 22 seconds after deasserting TX disable
before accessing the PHY. The code waits for 25 seconds just to be sure.

Signed-off-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>