UCT/MLX5: Initialize DP fields before creating command QP

[yosefe]

Why

Fix https://redmine.mellanox.com/issues/4246892

[ RUN      ] rcx/test_ucp_tag_match.send2_nb_recv_medium_wildcard/1 <rc_x/req_ext>
[1736352962.257227] [nemo03:678154:0]      ib_mlx5_dv.c:407  UCX  ERROR mlx5dv_devx_obj_modify(opcode=0x503) failed, syndrome 0x823f8d: Remote I/O error

[brminich]

maybe it is also worth to disable tag offload if ddp is enabled?

[yosefe]

maybe it is also worth to disable tag offload if ddp is enabled?

The issue happens on devices that don't have DDP, and create TM CMD QP.
I guess the bug happens when we run also on CX8 device, and happens to be a non-0 value in the un-initialized field.