drivers: uart_nrfx_uarte: Fix call to HW_RX_COUNTING_ENABLED()

Since the macro references `data->async->hw_rx_counting`, it cannot
be called when `data->async` is NULL, and this could happen when the
PM_DEVICE_ACTION_RESUME action was requested for an instance that uses
the interrupt-driven API while for another instance that uses the
asynchronous API the hardware counting of bytes was configured.
Prevent this by calling the macro from a proper `if` block.

Signed-off-by: Andrzej Głąbek <[email protected]>

Author: anangl

drivers/serial/uart_nrfx_uarte.c

@@ -1956,10 +1956,11 @@ static int uarte_nrfx_pm_action(const struct device *dev,
 		nrf_uarte_enable(uarte);
 
 #ifdef UARTE_ANY_ASYNC
-		if (HW_RX_COUNTING_ENABLED(data)) {
-			nrfx_timer_enable(&cfg->timer);
-		}
 		if (data->async) {
+			if (HW_RX_COUNTING_ENABLED(data)) {
+				nrfx_timer_enable(&cfg->timer);
+			}
+
 			return 0;
 		}
 #endif