[nrf fromtree] serial: nrfx_uarte: initial pin state to SLEEP

Configure the initial pin state of the UARTE peripheral to SLEEP, not
left uninitialised. This fixes the pin configuration not being set until
the interface is used if `zephyr,pm-device-runtime-auto` is enabled.

Signed-off-by: Jordan Yates <[email protected]>
(cherry picked from commit 69acc01)

Author: JordanYates

drivers/serial/uart_nrfx_uarte.c

@@ -2490,6 +2490,11 @@ static int uarte_instance_init(const struct device *dev,
 		((struct pinctrl_dev_config *)cfg->pcfg)->reg = (uintptr_t)cfg->uarte_regs;
 	}
 
+	/* Apply sleep state by default.
+	 * If PM is disabled, the default state will be applied in pm_device_driver_init.
+	 */
+	(void)pinctrl_apply_state(cfg->pcfg, PINCTRL_STATE_SLEEP);
+
 #ifdef CONFIG_UART_USE_RUNTIME_CONFIGURE
 	err = uarte_nrfx_configure(dev, &((struct uarte_nrfx_data *)dev->data)->uart_config);
 	if (err) {