drivers: mdio_nxp_enet: Don't disable IRQ

No real need to be enabling and disabling IRQs, this logic has been
reported to be causing spurious interrupts and strange behavior, we can
just enable the interrupt and switch to interrupt based logic one time
and keep the interrupt enabled at that point.

Also, fix a W1C bug where |= was used instead of = to clear a flag.

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>
(cherry picked from commit 2ab104625edcdfb05482566725fe1e7cc7c0548c)

drivers/mdio/mdio_nxp_enet.c

diff --git a/drivers/mdio/mdio_nxp_enet.c b/drivers/mdio/mdio_nxp_enet.c
index a506d83..05a67ac 100644
--- a/drivers/mdio/mdio_nxp_enet.c
+++ b/drivers/mdio/mdio_nxp_enet.c
@@ -41,17 +41,13 @@
 static int nxp_enet_mdio_wait_xfer(const struct device *dev)
 {
 	struct nxp_enet_mdio_data *data = dev->data;
-	ENET_Type *base = data->base;
 
 	/* This function will not make sense from IRQ context */
 	if (k_is_in_isr()) {
 		return -EWOULDBLOCK;
 	}
 
-	if (data->interrupt_up) {
-		/* Enable the interrupt */
-		base->EIMR |= ENET_EIMR_MII_MASK;
-	} else {
+	if (!data->interrupt_up) {
 		/* If the interrupt is not available to use yet, just busy wait */
 		k_busy_wait(CONFIG_MDIO_NXP_ENET_TIMEOUT);
 		k_sem_give(&data->mdio_sem);
@@ -77,7 +73,7 @@
 	 * Clear the bit (W1C) that indicates MDIO transfer is ready to
 	 * prepare to wait for it to be set once this read is done
 	 */
-	data->base->EIR |= ENET_EIR_MII_MASK;
+	data->base->EIR = ENET_EIR_MII_MASK;
 
 	/*
 	 * Write MDIO frame to MII management register which will
@@ -105,7 +101,7 @@
 	*read_data = (data->base->MMFR & ENET_MMFR_DATA_MASK) >> ENET_MMFR_DATA_SHIFT;
 
 	/* Clear the same bit as before because the event has been handled */
-	data->base->EIR |= ENET_EIR_MII_MASK;
+	data->base->EIR = ENET_EIR_MII_MASK;
 
 	/* This MDIO interaction is finished */
 	(void)k_mutex_unlock(&data->mdio_mutex);
@@ -127,7 +123,7 @@
 	 * Clear the bit (W1C) that indicates MDIO transfer is ready to
 	 * prepare to wait for it to be set once this write is done
 	 */
-	data->base->EIR |= ENET_EIR_MII_MASK;
+	data->base->EIR = ENET_EIR_MII_MASK;
 
 	/*
 	 * Write MDIO frame to MII management register which will
@@ -153,7 +149,7 @@
 	}
 
 	/* Clear the same bit as before because the event has been handled */
-	data->base->EIR |= ENET_EIR_MII_MASK;
+	data->base->EIR = ENET_EIR_MII_MASK;
 
 	/* This MDIO interaction is finished */
 	(void)k_mutex_unlock(&data->mdio_mutex);
@@ -170,13 +166,9 @@
 {
 	struct nxp_enet_mdio_data *data = dev->data;
 
-	data->base->EIR |= ENET_EIR_MII_MASK;
+	data->base->EIR = ENET_EIR_MII_MASK;
 
-	/* Signal that operation finished */
 	k_sem_give(&data->mdio_sem);
-
-	/* Disable the interrupt */
-	data->base->EIMR &= ~ENET_EIMR_MII_MASK;
 }
 
 static void nxp_enet_mdio_post_module_reset_init(const struct device *dev)
@@ -212,7 +204,9 @@
 		nxp_enet_mdio_isr_cb(dev);
 		break;
 	case NXP_ENET_INTERRUPT_ENABLED:
+		/* IRQ was enabled in NVIC, now enable in enet */
 		data->interrupt_up = true;
+		data->base->EIMR |= ENET_EIMR_MII_MASK;
 		break;
 	default:
 		break;