phy: sfp: add netlink SFP support to generic SFP code

The new netlink API for reading SFP data requires a new op to be
implemented. The idea of the new netlink SFP code is that userspace is
responsible to parsing the EEPROM data and requesting pages, rather
than have the kernel decide what pages are interesting and returning
them. This allows greater flexibility for newer formats.

Currently the generic SFP code only supports simple SFPs. Allow i2c
address 0x50 and 0x51 to be accessed with page and bank must always be
0. This interface will later be extended when for example QSFP support
is added.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Vladyslav Tarasiuk <vladyslavt@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>