modpost: do not call get_modinfo() for vmlinux(.o)

The three calls of get_modinfo() ("license", "import_ns", "version")
always return NULL for vmlinux(.o) because the built-in module info is
prefixed with __MODULE_INFO_PREFIX.

It is harmless to call get_modinfo(), but there is no point to search
for what apparently does not exist.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/mod/modpost.c

@@ -2006,25 +2006,26 @@ static void read_symbols(const char *modname)
 		mod->skip = 1;
 	}
 
-	license = get_modinfo(&info, "license");
-	if (!license && !is_vmlinux(modname))
-		warn("missing MODULE_LICENSE() in %s\n"
-		     "see include/linux/module.h for "
-		     "more information\n", modname);
-	while (license) {
-		if (license_is_gpl_compatible(license))
-			mod->gpl_compatible = 1;
-		else {
-			mod->gpl_compatible = 0;
-			break;
+	if (!is_vmlinux(modname)) {
+		license = get_modinfo(&info, "license");
+		if (!license)
+			warn("missing MODULE_LICENSE() in %s\n", modname);
+		while (license) {
+			if (license_is_gpl_compatible(license))
+				mod->gpl_compatible = 1;
+			else {
+				mod->gpl_compatible = 0;
+				break;
+			}
+			license = get_next_modinfo(&info, "license", license);
 		}
-		license = get_next_modinfo(&info, "license", license);
-	}
 
-	namespace = get_modinfo(&info, "import_ns");
-	while (namespace) {
-		add_namespace(&mod->imported_namespaces, namespace);
-		namespace = get_next_modinfo(&info, "import_ns", namespace);
+		namespace = get_modinfo(&info, "import_ns");
+		while (namespace) {
+			add_namespace(&mod->imported_namespaces, namespace);
+			namespace = get_next_modinfo(&info, "import_ns",
+						     namespace);
+		}
 	}
 
 	for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
@@ -2065,10 +2066,12 @@ static void read_symbols(const char *modname)
 	if (!is_vmlinux(modname) || vmlinux_section_warnings)
 		check_sec_ref(mod, modname, &info);
 
-	version = get_modinfo(&info, "version");
-	if (version || (all_versions && !is_vmlinux(modname)))
-		get_src_version(modname, mod->srcversion,
-				sizeof(mod->srcversion)-1);
+	if (!is_vmlinux(modname)) {
+		version = get_modinfo(&info, "version");
+		if (version || all_versions)
+			get_src_version(modname, mod->srcversion,
+					sizeof(mod->srcversion) - 1);
+	}
 
 	parse_elf_finish(&info);