kconfig: remove const qualifier from sym_expand_string_value()

This function returns realloc'ed memory, so the returned pointer
must be passed to free() when done.  So, 'const' qualifier is odd.
It is allowed to modify the expanded string.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

scripts/kconfig/lkc_proto.h

@@ -31,7 +31,7 @@ extern struct symbol * symbol_hash[SYMBOL_HASHSIZE];
 
 struct symbol * sym_lookup(const char *name, int flags);
 struct symbol * sym_find(const char *name);
-const char * sym_expand_string_value(const char *in);
+char *sym_expand_string_value(const char *in);
 const char * sym_escape_string_value(const char *in);
 struct symbol ** sym_re_search(const char *pattern);
 const char * sym_type_name(enum symbol_type type);

scripts/kconfig/symbol.c

@@ -899,7 +899,7 @@ struct symbol *sym_find(const char *name)
  * name to be expanded shall be prefixed by a '$'. Unknown symbol expands to
  * the empty string.
  */
-const char *sym_expand_string_value(const char *in)
+char *sym_expand_string_value(const char *in)
 {
 	const char *src;
 	char *res;

scripts/kconfig/util.c

@@ -14,11 +14,11 @@
 struct file *file_lookup(const char *name)
 {
 	struct file *file;
-	const char *file_name = sym_expand_string_value(name);
+	char *file_name = sym_expand_string_value(name);
 
 	for (file = file_list; file; file = file->next) {
 		if (!strcmp(name, file->name)) {
-			free((void *)file_name);
+			free(file_name);
 			return file;
 		}
 	}