net: phy: broadcom: remove BCM5482 1000Base-BX support

It is nowhere used in the kernel. It also seems to be lacking the
proper fiber advertise flags. Remove it.

Signed-off-by: Michael Walle <michael@walle.cc>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>