net: gemini: Clean up phy registration

It's nice if the phy is online before we register the netdev
so try to do that first.

Stop trying to do "second tried" to register the phy, it
works perfectly fine the first time.

Stop remvoving the phy in uninit. Remove it when the
driver is remove():d, symmetric to where it is added, in
probe().

Suggested-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reported-by: David Miller <davem@davemloft.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>