net: pcs: rzn1-miic: fill in PCS supported_interfaces

Populate the PCS supported_interfaces bitmap with the interfaces that
this PCS supports. This makes the manual checking in miic_validate()
redundant, so remove that.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/E1tfhYq-003aTm-Nx@rmk-PC.armlinux.org.uk


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