net: stmmac: remove xstats.pcs_* members

net: stmmac: remove xstats.pcs_* members

As a result of the previous commit, the pcs_link, pcs_duplex and
pcs_speed members are not used outside of the interrupt handling code,
and are only used to print their status using the misleading "Link is"
messages that bear no relation to the actual status of the link.

Remove the printing of these messages, these members, and the code
that decodes them from the hardware.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Tested-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://patch.msgid.link/E1v9P63-0000000AolI-23Kf@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>