net/mlx5: Fix read from coherent memory

Use accessor function READ_ONCE to read from coherent memory modified
by the device and read by the driver. This becomes most important in
preemptive kernels where cond_resched implementation does not have the
side effect which guaranteed the updated value.

Fixes: 269d26f4 ("net/mlx5: Reduce command polling interval")
Change-Id: Ie6deeb565ffaf76777b07448c7fbcce3510bbb8a
Signed-off-by: Eli Cohen <eli@mellanox.com>
Reported-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/cmd.c

@@ -206,7 +206,7 @@ static void poll_timeout(struct mlx5_cmd_work_ent *ent)
 	u8 own;
 
 	do {
-		own = ent->lay->status_own;
+		own = READ_ONCE(ent->lay->status_own);
 		if (!(own & CMD_OWNER_HW)) {
 			ent->ret = 0;
 			return;