dmaengine: tegra: Fix uninitialized variable usage

Initialize slave_bw in dma_prep*() functions as the parameter is not
set for DMA_MEM_TO_MEM case in get_transfer_param(). Though the case
may never occur, initializing it avoids warning from certain static
checkers

Fixes: ee17028009d4 ("dmaengine: tegra: Add tegra gpcdma driver")
Reported-by: Dan Carpenter <[e-mail]>
Signed-off-by: Akhil R <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/dma/tegra186-gpc-dma.c

···
 {
 	struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
 	unsigned int max_dma_count = tdc->tdma->chip_data->max_dma_count;
+	enum dma_slave_buswidth slave_bw = DMA_SLAVE_BUSWIDTH_UNDEFINED;
 	u32 csr, mc_seq, apb_ptr = 0, mmio_seq = 0;
-	enum dma_slave_buswidth slave_bw;
 	struct tegra_dma_sg_req *sg_req;
 	struct tegra_dma_desc *dma_desc;
 	struct scatterlist *sg;
···
 			  size_t period_len, enum dma_transfer_direction direction,
 			  unsigned long flags)
 {
+	enum dma_slave_buswidth slave_bw = DMA_SLAVE_BUSWIDTH_UNDEFINED;
+	u32 csr, mc_seq, apb_ptr = 0, mmio_seq = 0, burst_size;
+	unsigned int max_dma_count, len, period_count, i;
 	struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
 	struct tegra_dma_desc *dma_desc;
 	struct tegra_dma_sg_req *sg_req;
-	enum dma_slave_buswidth slave_bw;
-	u32 csr, mc_seq, apb_ptr = 0, mmio_seq = 0, burst_size;
-	unsigned int max_dma_count, len, period_count, i;
 	dma_addr_t mem = buf_addr;
 	int ret;