net: lan966x: move unnecessary linux/sfp.h include

lan966x_phylink.c doesn't make use of anything from linux/sfp.h, so
remove this unnecessary include.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/E1oqzx9-001r9g-HV@rmk-PC.armlinux.org.uk


Signed-off-by: Jakub Kicinski <kuba@kernel.org>