dmaengine: qcom: gpi: Fix memory leak in gpi_peripheral_config()

Fix a memory leak in gpi_peripheral_config() where the original memory
pointed to by gchan->config could be lost if krealloc() fails.

The issue occurs when:
1. gchan->config points to previously allocated memory
2. krealloc() fails and returns NULL
3. The function directly assigns NULL to gchan->config, losing the
reference to the original memory
4. The original memory becomes unreachable and cannot be freed

Fix this by using a temporary variable to hold the krealloc() result
and only updating gchan->config when the allocation succeeds.

Found via static analysis and code review.

Fixes: 5d0c3533a19f ("dmaengine: qcom: Add GPI dma driver")
Cc: [e-mail]
Signed-off-by: Miaoqian Lin <[e-mail]>
Reviewed-by: Bjorn Andersson <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/dma/qcom/gpi.c

···
 gpi_peripheral_config(struct dma_chan *chan, struct dma_slave_config *config)
 {
 	struct gchan *gchan = to_gchan(chan);
+	void *new_config;
 
 	if (!config->peripheral_config)
 		return -EINVAL;
 
-	gchan->config = krealloc(gchan->config, config->peripheral_size, GFP_NOWAIT);
-	if (!gchan->config)
+	new_config = krealloc(gchan->config, config->peripheral_size, GFP_NOWAIT);
+	if (!new_config)
 		return -ENOMEM;
 
+	gchan->config = new_config;
 	memcpy(gchan->config, config->peripheral_config, config->peripheral_size);
 
 	return 0;