net/mlx5e: IPoIB, Modify add/remove underlay QPN flows

On interface remove, the clean-up was done incorrectly causing
an error in the log:
"SET_FLOW_TABLE_ROOT(0x92f) op_mod(0x0) failed...syndrome (0x7e9f14)"

This was caused by the following flow:
-ndo_uninit:
 Move QP state to RST (this disconnects the QP from FT),
 the QP cannot be attached to any FT unless it is in RTS.

-mlx5_rdma_netdev_free:
 cleanup_rx: Destroy FT
 cleanup_tx: Destroy QP and remove QPN from FT

This caused a problem when destroying current FT we tried to
re-attach the QP to the next FT which is not needed.

The correct flow is:
-mlx5_rdma_netdev_free:
	cleanup_rx: remove QPN from FT & Destroy FT
	cleanup_tx: Destroy QP

Fixes: 50854114 ("net/mlx5: Use underlay QPN from the root name space")
Signed-off-by: Alex Vesker <valex@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>