dmaengine: xilinx_dma: remove set but not used variable 'tail_segment'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/dma/xilinx/xilinx_dma.c: In function 'xilinx_vdma_start_transfer':
drivers/dma/xilinx/xilinx_dma.c:1104:33: warning:
 variable 'tail_segment' set but not used [-Wunused-but-set-variable]

It not used since commit b8349172 ("dmaengine: xilinx_dma: Drop SG support
for VDMA IP")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/xilinx/xilinx_dma.c

@@ -1101,7 +1101,6 @@ static void xilinx_vdma_start_transfer(struct xilinx_dma_chan *chan)
 	struct xilinx_vdma_config *config = &chan->config;
 	struct xilinx_dma_tx_descriptor *desc, *tail_desc;
 	u32 reg, j;
-	struct xilinx_vdma_tx_segment *tail_segment;
 	struct xilinx_vdma_tx_segment *segment, *last = NULL;
 	int i = 0;
 
@@ -1120,9 +1119,6 @@ static void xilinx_vdma_start_transfer(struct xilinx_dma_chan *chan)
 	tail_desc = list_last_entry(&chan->pending_list,
 				    struct xilinx_dma_tx_descriptor, node);
 
-	tail_segment = list_last_entry(&tail_desc->segments,
-				       struct xilinx_vdma_tx_segment, node);
-
 	/* Configure the hardware using info in the config structure */
 	if (chan->has_vflip) {
 		reg = dma_read(chan, XILINX_VDMA_REG_ENABLE_VERTICAL_FLIP);