net: stmmac: move xpcs clause 73 test into stmmac_init_phy()

We avoid binding a PHY if the XPCS is using clause 73 negotiation.
Rather than having this complexity in __stmmac_open(), move it to
stmmac_init_phy() instead. There is no point checking the XPCS
state this unless phylink wants a PHY, so place this appropriately.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/E1v119o-0000000773y-21gs@rmk-PC.armlinux.org.uk


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