[nrf fromtree] drivers: mspi: mspi_dw: make sure controller is disabled at entry

Some systems (IE cores with bootloaders) may not disable the DW SPI
peripheral at boot time. Make sure the peripheral is disabled before we
try to configure it.

Signed-off-by: Daniel DeGrasse <[email protected]>
(cherry picked from commit a294653)

Author: danieldegrasse

drivers/mspi/mspi_dw.c

@@ -1437,6 +1437,9 @@ static int dev_init(const struct device *dev)
 		}
 	}
 
+	/* Make sure controller is disabled. */
+	write_ssienr(dev, 0);
+
 #if defined(CONFIG_PINCTRL)
 	if (IS_ENABLED(CONFIG_PM_DEVICE_RUNTIME)) {
 		rc = pinctrl_apply_state(dev_config->pcfg, PINCTRL_STATE_SLEEP);