mdio_bus: fix mdio_register_device when RESET_CONTROLLER is disabled

When CONFIG_RESET_CONTROLLER is disabled, the
devm_reset_control_get_exclusive function returns -ENOTSUPP. This is not
handled in subsequent check and then the mdio device fails to probe.

When CONFIG_RESET_CONTROLLER is enabled, its code checks in OF for reset
device, and since it is not present, returns -ENOENT. -ENOENT is handled.
Add -ENOTSUPP also.

This happened to me when upgrading kernel on Turris Omnia. You either
have to enable CONFIG_RESET_CONTROLLER or use this patch.

Signed-off-by: Marek Behún <[e-mail]>
Fixes: 71dd6c0dff51b ("net: phy: add support for reset-controller")
Cc: Dmitry Torokhov <[e-mail]>
Cc: Andrew Lunn <[e-mail]>
Cc: Andy Shevchenko <[e-mail]>
Reviewed-by: Andrew Lunn <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/phy/mdio_bus.c

···
 		reset = devm_reset_control_get_exclusive(&mdiodev->dev,
 							 "phy");
 	if (IS_ERR(reset)) {
-		if (PTR_ERR(reset) == -ENOENT || PTR_ERR(reset) == -ENOSYS)
+		if (PTR_ERR(reset) == -ENOENT || PTR_ERR(reset) == -ENOSYS ||
+		    PTR_ERR(reset) == -ENOTSUPP)
 			reset = NULL;
 		else
 			return PTR_ERR(reset);