net: dsa: microchip: Refactor switch shutdown routine for WoL preparation

Centralize the switch shutdown routine in a dedicated function,
ksz_switch_shutdown(), to enhance code maintainability and reduce
redundancy. This change abstracts the common shutdown operations
previously duplicated in ksz9477_i2c_shutdown() and ksz_spi_shutdown().

This refactoring is a preparatory step for an upcoming patch to avoid
reset on shutdown if Wake-on-LAN (WoL) is enabled.

Signed-off-by: Oleksij Rempel <[e-mail]>
Reviewed-by: Florian Fainelli <[e-mail]>
Reviewed-by: Vladimir Oltean <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/dsa/microchip/ksz9477_i2c.c

···
 	if (!dev)
 		return;
 
-	if (dev->dev_ops->reset)
-		dev->dev_ops->reset(dev);
-
-	dsa_switch_shutdown(dev->ds);
+	ksz_switch_shutdown(dev);
 
 	i2c_set_clientdata(i2c, NULL);
 }

drivers/net/dsa/microchip/ksz_common.c

···
 }
 EXPORT_SYMBOL(ksz_switch_alloc);
 
+/**
+ * ksz_switch_shutdown - Shutdown routine for the switch device.
+ * @dev: The switch device structure.
+ *
+ * This function is responsible for initiating a shutdown sequence for the
+ * switch device. It invokes the reset operation defined in the device
+ * operations, if available, to reset the switch. Subsequently, it calls the
+ * DSA framework's shutdown function to ensure a proper shutdown of the DSA
+ * switch.
+ */
+void ksz_switch_shutdown(struct ksz_device *dev)
+{
+	if (dev->dev_ops->reset)
+		dev->dev_ops->reset(dev);
+
+	dsa_switch_shutdown(dev->ds);
+}
+EXPORT_SYMBOL(ksz_switch_shutdown);
+
 static void ksz_parse_rgmii_delay(struct ksz_device *dev, int port_num,
 				  struct device_node *port_dn)
 {

drivers/net/dsa/microchip/ksz_common.h

···
 int ksz_switch_macaddr_get(struct dsa_switch *ds, int port,
 			   struct netlink_ext_ack *extack);
 void ksz_switch_macaddr_put(struct dsa_switch *ds);
+void ksz_switch_shutdown(struct ksz_device *dev);
 
 /* Common register access functions */
 static inline struct regmap *ksz_regmap_8(struct ksz_device *dev)

drivers/net/dsa/microchip/ksz_spi.c

···
 	if (!dev)
 		return;
 
-	if (dev->dev_ops->reset)
-		dev->dev_ops->reset(dev);
-
-	dsa_switch_shutdown(dev->ds);
+	ksz_switch_shutdown(dev);
 
 	spi_set_drvdata(spi, NULL);
 }