b43: allocate receive buffers big enough for max frame len + offset

Otherwise, skb_put inside of dma_rx can fail...

	https://bugzilla.kernel.org/show_bug.cgi?id=32042

Signed-off-by: John W. Linville <linville@tuxdriver.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: stable@kernel.org
static inline int free_slots(struct b43_dmaring *ring)
{
	return (ring->nr_slots - ring->used_slots);
}

static inline int free_slots(struct b43_dmaring *ring)
{
	return (ring->nr_slots - ring->used_slots);
}
