net: sfp: move fwnode parsing into sfp-bus layer

Rather than parsing the sfp firmware node in phylink, parse it in the
sfp-bus code, so we can re-use this code for PHYs without having to
duplicate the parsing.

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