net: stmmac: remove SGMII/RGMII/SMII interrupt handling

net: stmmac: remove SGMII/RGMII/SMII interrupt handling

Now that the only use for the interrupt is to clear it and increment a
statistic counter (which is not that relevant anymore) remove all this
code and ensure that the interrupt remains disabled to avoid a stuck
interrupt.

dwmac-sun8i still uses this statistic counter, so it is inappropriate
for this patch to remove it.

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/E1v9P68-0000000AolO-2W5s@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>