IB/mlx5: Fix fall-through warnings for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix a warning
by explicitly adding the new pseudo-keyword fallthrough; instead of
letting the code fall through to the next case.

Link: https://lore.kernel.org/r/2b0c87362bc86f6adfe56a5a6685837b71022bbf.1605896059.git.gustavoars@kernel.org
Link: https://github.com/KSPP/linux/issues/115Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Acked-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/hw/mlx5/qp.c

@@ -2434,6 +2434,7 @@ static int check_qp_type(struct mlx5_ib_dev *dev, struct ib_qp_init_attr *attr,
 	case IB_QPT_GSI:
 		if (dev->profile == &raw_eth_profile)
 			goto out;
+		fallthrough;
 	case IB_QPT_RAW_PACKET:
 	case IB_QPT_UD:
 	case MLX5_IB_QPT_REG_UMR: