kconfig: make xfgets() really static

Sparse reports:
  warning: symbol 'xfgets' was not declared. Should it be static?

It is declared as static, but it is missing in the definition part.
Move the definition up and remove the forward declaration.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/kconfig/conf.c

@@ -20,7 +20,6 @@
 
 static void conf(struct menu *menu);
 static void check_conf(struct menu *menu);
-static void xfgets(char *str, int size, FILE *in);
 
 enum input_mode {
 	oldaskconfig,
@@ -83,6 +82,13 @@ static void check_stdin(void)
 	}
 }
 
+/* Helper function to facilitate fgets() by Jean Sacren. */
+static void xfgets(char *str, int size, FILE *in)
+{
+	if (!fgets(str, size, in))
+		fprintf(stderr, "\nError in reading or end of file.\n");
+}
+
 static int conf_askvalue(struct symbol *sym, const char *def)
 {
 	enum symbol_type type = sym_get_type(sym);
@@ -713,12 +719,3 @@ int main(int ac, char **av)
 	}
 	return 0;
 }
-
-/*
- * Helper function to facilitate fgets() by Jean Sacren.
- */
-void xfgets(char *str, int size, FILE *in)
-{
-	if (fgets(str, size, in) == NULL)
-		fprintf(stderr, "\nError in reading or end of file.\n");
-}