net: phy: micrel: fix shared interrupt on LAN8814

Since commit ece19502 ("net: phy: micrel: 1588 support for LAN8814
phy") the handler always returns IRQ_HANDLED, except in an error case.
Before that commit, the interrupt status register was checked and if
it was empty, IRQ_NONE was returned. Restore that behavior to play nice
with the interrupt line being shared with others.

Fixes: ece19502 ("net: phy: micrel: 1588 support for LAN8814 phy")
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Reviewed-by: Divya Koppera <Divya.Koppera@microchip.com>
Link: https://lore.kernel.org/r/20220920141619.808117-1-michael@walle.ccSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/micrel.c

@@ -2679,16 +2679,19 @@ static int lan8804_config_init(struct phy_device *phydev)
 static irqreturn_t lan8814_handle_interrupt(struct phy_device *phydev)
 {
 	int irq_status, tsu_irq_status;
+	int ret = IRQ_NONE;
 
 	irq_status = phy_read(phydev, LAN8814_INTS);
-	if (irq_status > 0 && (irq_status & LAN8814_INT_LINK))
-		phy_trigger_machine(phydev);
-
 	if (irq_status < 0) {
 		phy_error(phydev);
 		return IRQ_NONE;
 	}
 
+	if (irq_status & LAN8814_INT_LINK) {
+		phy_trigger_machine(phydev);
+		ret = IRQ_HANDLED;
+	}
+
 	while (1) {
 		tsu_irq_status = lanphy_read_page_reg(phydev, 4,
 						      LAN8814_INTR_STS_REG);
@@ -2697,12 +2700,15 @@ static irqreturn_t lan8814_handle_interrupt(struct phy_device *phydev)
 		    (tsu_irq_status & (LAN8814_INTR_STS_REG_1588_TSU0_ |
 				       LAN8814_INTR_STS_REG_1588_TSU1_ |
 				       LAN8814_INTR_STS_REG_1588_TSU2_ |
-				       LAN8814_INTR_STS_REG_1588_TSU3_)))
+				       LAN8814_INTR_STS_REG_1588_TSU3_))) {
 			lan8814_handle_ptp_interrupt(phydev);
-		else
+			ret = IRQ_HANDLED;
+		} else {
 			break;
+		}
 	}
-	return IRQ_HANDLED;
+
+	return ret;
 }
 
 static int lan8814_ack_interrupt(struct phy_device *phydev)