net: ehernet: ixp4xx: Use netdev_* messages

Simplify and correct a bunch of messages using printk
directly to use the netdev_* macros. I have not changed
all of them, just the low-hanging fruit.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>