dmaengine: dw-axi-dmac: remove redundant null check on desc

The pointer desc is being null checked twice, the second null check
is redundant because desc has not been re-assigned between the
checks. Remove the redundant second null check on desc.

Fixes: ef6fb2d6f1 ("dmaengine: dw-axi-dmac: simplify descriptor management")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Tested-by: Sia Jee Heng <jee.heng.sia@intel.com>
Reviewed-by: Sia Jee Heng <jee.heng.sia@intel.com>
Addresses-Coverity: ("Logically dead code")
Link: https://lore.kernel.org/r/20210203134652.22618-1-colin.king@canonical.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c

@@ -919,10 +919,6 @@ dma_chan_prep_dma_memcpy(struct dma_chan *dchan, dma_addr_t dst_adr,
 		num++;
 	}
 
-	/* Total len of src/dest sg == 0, so no descriptor were allocated */
-	if (unlikely(!desc))
-		return NULL;
-
 	/* Set end-of-link to the last link descriptor of list */
 	set_desc_last(&desc->hw_desc[num - 1]);
 	/* Managed transfer list */