ALSA: core: Enable proc module when CONFIG_MODULES=y

We used '#ifdef MODULE' for judging whether the system supports the
sound module or not, and /proc/asound/modules is created only when
'#ifdef MODULE' is true.  The check is not really appropriate, though,
because the flag means only for the sound core and the drivers are
still allowed to be built as modules even if 'MODULE' is not set in
sound/core/init.c.

For fixing the inconsistency, replace those ifdefs with 'ifdef
CONFIG_MODULES'.  One place for a NULL module check is rewritten with
IS_MODULE(CONFIG_SND) to be more intuitive.  It can't be changed to
CONFIG_MODULES; otherwise it would hit a WARN_ON() incorrectly.

This is a slight behavior change; the modules proc entry appears now
no matter whether the sound core is built-in or not as long as modules
are enabled on the kernel in general.  This can't be avoided due to
the nature of kernel builds.

Link: https://lore.kernel.org/r/20240520170349.2417900-1-xu.yang_2@nxp.comSigned-off-by: Takashi Iwai <tiwai@suse.de>
Tested-by: Xu Yang <xu.yang_2@nxp.com>
Link: https://lore.kernel.org/r/20240522070442.17786-2-tiwai@suse.de

sound/core/init.c

@@ -50,7 +50,7 @@ MODULE_PARM_DESC(slots, "Module names assigned to the slots.");
 static int module_slot_match(struct module *module, int idx)
 {
 	int match = 1;
-#ifdef MODULE
+#ifdef CONFIG_MODULES
 	const char *s1, *s2;
 
 	if (!module || !*module->name || !slots[idx])
@@ -77,7 +77,7 @@ static int module_slot_match(struct module *module, int idx)
 		if (!c1)
 			break;
 	}
-#endif /* MODULE */
+#endif /* CONFIG_MODULES */
 	return match;
 }
 
@@ -311,9 +311,7 @@ static int snd_card_init(struct snd_card *card, struct device *parent,
 	}
 	card->dev = parent;
 	card->number = idx;
-#ifdef MODULE
-	WARN_ON(!module);
-#endif
+	WARN_ON(IS_MODULE(CONFIG_SND) && !module);
 	card->module = module;
 	INIT_LIST_HEAD(&card->devices);
 	init_rwsem(&card->controls_rwsem);
@@ -969,7 +967,7 @@ void snd_card_info_read_oss(struct snd_info_buffer *buffer)
 
 #endif
 
-#ifdef MODULE
+#ifdef CONFIG_MODULES
 static void snd_card_module_info_read(struct snd_info_entry *entry,
 				      struct snd_info_buffer *buffer)
 {
@@ -997,7 +995,7 @@ int __init snd_card_info_init(void)
 	if (snd_info_register(entry) < 0)
 		return -ENOMEM; /* freed in error path */
 
-#ifdef MODULE
+#ifdef CONFIG_MODULES
 	entry = snd_info_create_module_entry(THIS_MODULE, "modules", NULL);
 	if (!entry)
 		return -ENOMEM;