tests: net: socketpair: Fix log printing

The LOG_MODULE_REGISTER() was not called anywhere so if one tried
to enable logging, there was a linker error about missing logger
functions.

Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>

tests/net/socket/socketpair/src/_main.c

@@ -4,8 +4,12 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+#define _main_defined 1
+
 #include "_main.h"
 
+LOG_MODULE_REGISTER(net_test, CONFIG_NET_SOCKETS_LOG_LEVEL);
+
 #include <zephyr/logging/log.h>
 #include <zephyr/net/socket.h>
 #include <zephyr/ztest.h>

tests/net/socket/socketpair/src/_main.h

@@ -16,7 +16,9 @@
 #include <zephyr/sys/util.h>
 #include <zephyr/ztest.h>
 
+#if !defined(_main_defined)
 LOG_MODULE_DECLARE(net_test, CONFIG_NET_SOCKETS_LOG_LEVEL);
+#endif
 
 struct net_socketpair_fixture {
 	int sv[2];