[nrf fromtree] drivers: ieee802154: fix handling of struct ieee802154_config

`struct ieee802154_config config` is a struct containing an
union. Members of `config` were accessed incorrectly in
`otPlatRadioEnableCsl`. Fix by initializing `config` with `0`
and accessing one member at a time.

Signed-off-by: Maciej Baczmanski <[email protected]>
(cherry picked from commit 36b7f44)

Author: maciejbaczmanski

modules/openthread/platform/radio.c

@@ -1255,10 +1255,7 @@ void otPlatRadioSetMacFrameCounterIfLarger(otInstance *aInstance, uint32_t aMacF
 otError otPlatRadioEnableCsl(otInstance *aInstance, uint32_t aCslPeriod, otShortAddress aShortAddr,
 			     const otExtAddress *aExtAddr)
 {
-	struct ieee802154_config config = {
-		.ack_ie.short_addr = aShortAddr,
-		.ack_ie.ext_addr = aExtAddr->m8,
-	};
+	struct ieee802154_config config = { 0 };
 	int result;
 
 	ARG_UNUSED(aInstance);
@@ -1271,6 +1268,8 @@ otError otPlatRadioEnableCsl(otInstance *aInstance, uint32_t aCslPeriod, otShort
 	if (result) {
 		return OT_ERROR_FAILED;
 	}
+	config.ack_ie.short_addr = aShortAddr;
+	config.ack_ie.ext_addr = aExtAddr != NULL ? aExtAddr->m8 : NULL;
 
 	/* Configure the CSL IE. */
 	if (aCslPeriod > 0) {