sg_init_table() should use unsigned loop index variable

Clean up: fix a mixed sign comparison in sg_init_table() accidentally
introduced by commit d6ec0842.  The sign of the loop index variable
should match the sign of the "nents" argument.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Jens Axboe <axboe@carl.home.kernel.dk>

include/linux/scatterlist.h

@@ -243,7 +243,7 @@ static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents)
 	sg_mark_end(sgl, nents);
 #ifdef CONFIG_DEBUG_SG
 	{
-		int i;
+		unsigned int i;
 		for (i = 0; i < nents; i++)
 			sgl[i].sg_magic = SG_MAGIC;
 	}