mlx4_core: Fix setting VL_cap in mlx4_SET_PORT wrapper flow

Commit 096335b3f983 ("mlx4_core: Allow dynamic MTU configuration for
IB ports") modifies the port VL setting.  This exposes a bug in
mlx4_common_set_port(), where the VL cap value passed in (inside the
command mailbox) is incorrectly zeroed-out:

mlx4_SET_PORT modifies the VL_cap field (byte 3 of the mailbox).
Since the SET_PORT command is paravirtualized on the master as well as
on the slaves, mlx4_SET_PORT_wrapper() is invoked on the master.  This
calls mlx4_common_set_port() where mailbox byte 3 gets overwritten by
code which should only set a single bit in that byte (for the reset
qkey counter flag) -- but instead overwrites the entire byte.

The result is that when running in SR-IOV mode, the VL_cap will be set
to zero -- fix this.

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/net/ethernet/mellanox/mlx4/port.c

@@ -697,10 +697,10 @@ static int mlx4_common_set_port(struct mlx4_dev *dev, int slave, u32 in_mod,
 	if (slave != dev->caps.function)
 		memset(inbox->buf, 0, 256);
 	if (dev->flags & MLX4_FLAG_OLD_PORT_CMDS) {
-		*(u8 *) inbox->buf	   = !!reset_qkey_viols << 6;
+		*(u8 *) inbox->buf	   |= !!reset_qkey_viols << 6;
 		((__be32 *) inbox->buf)[2] = agg_cap_mask;
 	} else {
-		((u8 *) inbox->buf)[3]     = !!reset_qkey_viols;
+		((u8 *) inbox->buf)[3]     |= !!reset_qkey_viols;
 		((__be32 *) inbox->buf)[1] = agg_cap_mask;
 	}