The 'XFP' driver is really a driver for the QT2022C2 and QT2025C PHYs,
covering both more and less than XFP.  Rename its functions and
constants to reflect reality and to reduce namespace pollution when
sfc is a built-in driver.
Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>