kconfig: drop 'boolean' keyword

No more users of this keyword.  Drop it according to the notice by
commit 6341e62b21 ("kconfig: use bool instead of boolean for type
definition attributes").

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Luis R. Rodriguez <mcgrof@kernel.org>

scripts/kconfig/zconf.y

@@ -639,7 +639,7 @@ static void print_symbol(FILE *out, struct menu *menu)
 		fprintf(out, "\nconfig %s\n", sym->name);
 	switch (sym->type) {
 	case S_BOOLEAN:
-		fputs("  boolean\n", out);
+		fputs("  bool\n", out);
 		break;
 	case S_TRISTATE:
 		fputs("  tristate\n", out);