Commit 6341e62b ("kconfig: use bool instead of boolean for type
definition attributes") did treewide replacement of 'boolean', and
also mentioned the keyword 'boolean' would be dropped later on.

Some years have passed, but it has not happened yet.  Meanwhile, some
new instances have come up.

I am really going to drop this keyword.  I need to do the replacement
once again.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>