RDMA/SA: Fix kernel panic in CMA request handler flow

Commit 9fdca4da (IB/SA: Split struct sa_path_rec based on IB and
ROCE specific fields) moved the service_id to be specific attribute
for IB and OPA SA Path Record, and thus wasn't assigned for RoCE.

This caused to the following kernel panic in the CMA request handler flow:

[   27.074594] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
[   27.074731] IP: __radix_tree_lookup+0x1d/0xe0
...
[   27.075356] Workqueue: ib_cm cm_work_handler [ib_cm]
[   27.075401] task: ffff88022e3b8000 task.stack: ffffc90001298000
[   27.075449] RIP: 0010:__radix_tree_lookup+0x1d/0xe0
...
[   27.075979] Call Trace:
[   27.076015]  radix_tree_lookup+0xd/0x10
[   27.076055]  cma_ps_find+0x59/0x70 [rdma_cm]
[   27.076097]  cma_id_from_event+0xd2/0x470 [rdma_cm]
[   27.076144]  ? ib_init_ah_from_path+0x39a/0x590 [ib_core]
[   27.076193]  cma_req_handler+0x25/0x480 [rdma_cm]
[   27.076237]  cm_process_work+0x25/0x120 [ib_cm]
[   27.076280]  ? cm_get_bth_pkey.isra.62+0x3c/0xa0 [ib_cm]
[   27.076350]  cm_req_handler+0xb03/0xd40 [ib_cm]
[   27.076430]  ? sched_clock_cpu+0x11/0xb0
[   27.076478]  cm_work_handler+0x194/0x1588 [ib_cm]
[   27.076525]  process_one_work+0x160/0x410
[   27.076565]  worker_thread+0x137/0x4a0
[   27.076614]  kthread+0x112/0x150
[   27.076684]  ? max_active_store+0x60/0x60
[   27.077642]  ? kthread_park+0x90/0x90
[   27.078530]  ret_from_fork+0x2c/0x40

This patch moves it back to the common SA Path Record structure
and removes the redundant setter and getter.

Tested on Connect-IB and Connect-X4 in Infiniband and RoCE respectively.

Fixes: 9fdca4da

 (IB/SA: Split struct sa_path_rec based on IB ands
	ROCE specific fields)
Signed-off-by: Majd Dibbiny <majd@mellanox.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>