Friendship is a relationship. You can be in relationship with a few people. Friendliness is a quality not a relationship. It has nothing to do with anybody else; it is basically your inner quality. You can be friendly even when you are alone. You cannot be in friendship when you are alone - the other is needed - but friendliness is a kind of fragrance. A flower opens in the jungle; nobody passes by - still it is fragrant. It does not matter whether anybody comes to know of it or not, it is its quality. Nobody may ever come to know about it, but that does not matter. The flower is rejoicing.
Friendship can exist only between one man and another man or at the most between a man and an animal - a horse, a dog. But friendliness can exist even with a rock, with a river, with a mountain, with a cloud, with a far-away star. Friendliness is unlimited because it is not dependent on the other; it is absolutely your own flowering.
So, be friendly, just friendly to all that exists. And in that friendliness you will find all that is worth finding. In friendliness you will find the ultimate friend.