net: fman_memac: use lynx_pcs_create_fwnode()

Use lynx_pcs_create_fwnode() to create a lynx PCS from a fwnode handle.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>