net/mlx5e: Don't modify CQ before it was created

net/mlx5e: Don't modify CQ before it was created

BugLink: http://bugs.launchpad.net/bugs/1557950
Calling mlx5e_set_coalesce while the interface is down will result in
modifying CQs that don't exist.

Fixes: f62b8bb8f2d3 ('net/mlx5: Extend mlx5_core to support ConnectX-4
Ethernet functionality')
Signed-off-by: Gal Pressman <galp@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from linux-next commit 2fcb92fbd04eef26dfe7e67839da6262d83d6b65)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>