lan743x: remove redundant initialization of variable current_head_index

The variable current_head_index is being initialized with a value that
is never read and it is being updated later with a new value.  Replace
the initialization of -1 with the latter assignment.

Addresses-Coverity: ("Unused value")
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/microchip/lan743x_main.c

@@ -2046,14 +2046,13 @@ static int lan743x_rx_process_packet(struct lan743x_rx *rx)
 {
 	struct skb_shared_hwtstamps *hwtstamps = NULL;
 	int result = RX_PROCESS_RESULT_NOTHING_TO_DO;
+	int current_head_index = *rx->head_cpu_ptr;
 	struct lan743x_rx_buffer_info *buffer_info;
 	struct lan743x_rx_descriptor *descriptor;
-	int current_head_index = -1;
 	int extension_index = -1;
 	int first_index = -1;
 	int last_index = -1;
 
-	current_head_index = *rx->head_cpu_ptr;
 	if (current_head_index < 0 || current_head_index >= rx->ring_size)
 		goto done;