r8169: remove unused variable

#define TX_BUFFS_AVAIL(tp) \

	(tp->dirty_tx + NUM_TX_DESC - tp->cur_tx - 1)

/* Maximum events (Rx packets, etc.) to handle at each interrupt. */

static const int max_interrupt_work = 20;

/* Maximum number of multicast addresses to filter (vs. Rx-all-multicast).

   The RTL chips use a 64 element hash table based on the Ethernet CRC. */

static const int multicast_filter_limit = 32;