net: sfp: ignore power level 2 prior to SFF-8472 Rev 10.2

Power level 2 was introduced by SFF-8472 revision 10.2. Ignore
the power declaration bit for modules that are not compliant with
at least this revision.

This should remove any spurious indication of 1.5W modules.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>