SG: clear termination bit in sg_chain()

Since we are using the last entry in the list, clear any possible
termination bit that may have already been set. Pointed out by Rusty.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

include/linux/scatterlist.h

@@ -179,7 +179,11 @@ static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
 #ifndef ARCH_HAS_SG_CHAIN
 	BUG();
 #endif
-	prv[prv_nents - 1].page_link = (unsigned long) sgl | 0x01;
+	/*
+	 * Set lowest bit to indicate a link pointer, and make sure to clear
+	 * the termination bit if it happens to be set.
+	 */
+	prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
 }
 
 /**