dmaengine: xilinx: xdma: Fix initialization location of desc in xdma_channel_isr()

Clang warns (or errors with CONFIG_WERROR=y):

  drivers/dma/xilinx/xdma.c:894:3: error: variable 'desc' is uninitialized when used here [-Werror,-Wuninitialized]
    894 |                 desc->error = true;
        |                 ^~~~

The initialization of desc was moved too far forward, move it back so
that this assignment does not result in a potential crash at runtime
while clearing up the warning.

Closes: ClangBuiltLinux#1972
Fixes: 2f8f90c ("dmaengine: xilinx: xdma: Implement interleaved DMA transfers")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20231222-dma-xilinx-xdma-clang-fixes-v1-2-84a18ff184d2@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: nathanchance

drivers/dma/xilinx/xdma.c

@@ -888,6 +888,8 @@ static irqreturn_t xdma_channel_isr(int irq, void *dev_id)
 	if (ret)
 		goto out;
 
+	desc = to_xdma_desc(vd);
+
 	st &= XDMA_CHAN_STATUS_MASK;
 	if ((st & XDMA_CHAN_ERROR_MASK) ||
 	    !(st & (CHAN_CTRL_IE_DESC_COMPLETED | CHAN_CTRL_IE_DESC_STOPPED))) {
@@ -901,7 +903,6 @@ static irqreturn_t xdma_channel_isr(int irq, void *dev_id)
 	if (ret)
 		goto out;
 
-	desc = to_xdma_desc(vd);
 	if (desc->interleaved_dma) {
 		xchan->busy = false;
 		desc->completed_desc_num += complete_desc_num;