crypto: cavium/nitrox - Remove redundant initialization of 'sg'

Pointer 'sg' is being initialized however this value is never
read as 'sg' is assigned a same value in for_each_sg().
Remove the redundant assignment.

Cleans up clang warning:

drivers/crypto/cavium/nitrox/nitrox_reqmgr.c:161:22: warning: Value
stored to 'sg' during its initialization is never read
[clang-analyzer-deadcode.DeadStores]
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/cavium/nitrox/nitrox_reqmgr.c

@@ -159,7 +159,7 @@ static int dma_map_inbufs(struct nitrox_softreq *sr,
 			  struct se_crypto_request *req)
 {
 	struct device *dev = DEV(sr->ndev);
-	struct scatterlist *sg = req->src;
+	struct scatterlist *sg;
 	int i, nents, ret = 0;
 
 	nents = dma_map_sg(dev, req->src, sg_nents(req->src),