IB/srp: Fix srp_map_sg_fr()

After dma_map_sg() has been called the return value of that function
must be used as the number of elements in the scatterlist instead of
scsi_sg_count().

Fixes: commit f7f7aab1a5c0 ("IB/srp: Convert to new registration API")
Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: stable <stable@vger.kernel.org> # v4.4+
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Sebastian Parschauer <sebastian.riemer@profitbricks.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
diff --git a/drivers/infiniband/ulp/srp/ib_srp.h b/drivers/infiniband/ulp/srp/ib_srp.h
index 87a2a91..f6af531 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.h
+++ b/drivers/infiniband/ulp/srp/ib_srp.h
@@ -300,10 +300,7 @@
 	dma_addr_t		base_dma_addr;
 	u32			dma_len;
 	u32			total_len;
-	union {
-		unsigned int	npages;
-		int		sg_nents;
-	};
+	unsigned int		npages;
 	unsigned int		nmdesc;
 	unsigned int		ndesc;
 };