gnss(septentrio): fix error on driver start with same device paths

This fixes an incorrect check of the device paths during instantiation
of the Septentrio driver that caused the driver to start and not print
an error message.

src/drivers/gnss/septentrio/septentrio.cpp

@@ -432,7 +432,7 @@ SeptentrioDriver *SeptentrioDriver::instantiate(int argc, char *argv[], Instance
 	}
 
 	if (arguments.device_path_main && arguments.device_path_secondary
-	    && arguments.device_path_main == arguments.device_path_secondary) {
+	    && strcmp(arguments.device_path_main, arguments.device_path_secondary) == 0) {
 		mavlink_log_critical(&k_mavlink_log_pub, "Septentrio: Device paths must be different");
 		return nullptr;
 	}