drivers: nrf_wifi: Fix return value for getting current reg domain

It is observed that the regulatory domain API returns a failure
even when it has successfully completed its task. This change
addresses a minor fix to return the proper value to the user
when attempting to set the regulatory domain.

Signed-off-by: Vivekananda Uppunda <vivekananda.uppunda@nordicsemi.no>

Author: VivekUppunda

drivers/wifi/nrf_wifi/src/fmac_main.c

@@ -357,6 +357,7 @@ int nrf_wifi_reg_domain(const struct device *dev, struct wifi_reg_domain *reg_do
 			goto out;
 		}
 
+		ret = 0;
 		goto out;
 	}
 #endif