net/mlx5e: Cancel DIM work on close SQ

TXQ SQ closure is followed by closing the corresponding CQ. A pending
DIM work would try to modify the now non-existing CQ.
This would trigger an error:
[85535.835926] mlx5_core 0000:af:00.0: mlx5_cmd_check:769:(pid 124399):
MODIFY_CQ(0x403) op_mod(0x0) failed, status bad resource state(0x9), syndrome (0x1d7771)

Fix by making sure to cancel any pending DIM work before destroying the SQ.

Fixes: cbce4f44 ("net/mlx5e: Enable adaptive-TX moderation")
Signed-off-by: Tal Gilboa <talgi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>