net: phylink: validate sfp_select_interface() returned interface

net: phylink: validate sfp_select_interface() returned interface

Validate that the returned interface from sfp_select_interface() is
supportable by the MAC/PCS. If it isn't, print an error and return
the NA interface type. This is a preparatory step to reorganising
how a PHY on a SFP module is handled.

Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Tested-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1t3bcV-000c8B-Vz@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>