net: phy: micrel: Remove ksz90x1 drivers from micrel_ksz8xxx

There should be no longer be any ksz9000 users that pick up the PHY
driver from ksz8xxx, so remove ksz9000 remnants from there.

Signed-off-by: Alexandru Gagniuc <alex.g@adaptrum.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>