sfc: remove unused 'refcnt' from efx_rx_page_state

 * Used to facilitate sharing dma mappings between recycled rx buffers

 * and those passed up to the kernel.

 *

 * @refcnt: Number of struct efx_rx_buffer's referencing this page.

 *	When refcnt falls to zero, the page is unmapped for dma

 * @dma_addr: The dma address of this page.

 */

struct efx_rx_page_state {

	unsigned refcnt;

	dma_addr_t dma_addr;

	unsigned int __pad[0] ____cacheline_aligned;