RDMA/mlx5: Fix unsafe xarray access in implicit ODP handling

In the Linux kernel, the following vulnerability has been resolved:

RDMA/mlx5: Fix unsafe xarray access in implicit ODP handling

__xa_store() and __xa_erase() were used without holding the proper lock,
which led to a lockdep warning due to unsafe RCU usage. This patch
replaces them with xa_store() and xa_erase(), which perform the necessary
locking internally.

=============================
WARNING: suspicious RCPU usage
6.14.0-rc7_for_upstream_debug_2025_03_18_15_01 #1 Not tainted
-----------------------------
./include/linux/xarray.h:1211 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
3 locks held by kworker/u136:0/219:
at: process_one_work+0xbe4/0x15f0
process_one_work+0x75c/0x15f0
pagefault_mr+0x9a5/0x1390 [mlx5_ib]

stack backtrace:
CPU: 14 UID: 0 PID: 219 Comm: kworker/u136:0 Not tainted
6.14.0-rc7_for_upstream_debug_2025_03_18_15_01 #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
Workqueue: mlx5_ib_page_fault mlx5_ib_eqe_pf_action [mlx5_ib]
Call Trace:
dump_stack_lvl+0xa8/0xc0
lockdep_rcu_suspicious+0x1e6/0x260
xas_create+0xb8a/0xee0
xas_store+0x73/0x14c0
__xa_store+0x13c/0x220
? xa_store_range+0x390/0x390
? spin_bug+0x1d0/0x1d0
pagefault_mr+0xcb5/0x1390 [mlx5_ib]
? _raw_spin_unlock+0x1f/0x30
mlx5_ib_eqe_pf_action+0x3be/0x2620 [mlx5_ib]
? lockdep_hardirqs_on_prepare+0x400/0x400
? mlx5_ib_invalidate_range+0xcb0/0xcb0 [mlx5_ib]
process_one_work+0x7db/0x15f0
? pwq_dec_nr_in_flight+0xda0/0xda0
? assign_work+0x168/0x240
worker_thread+0x57d/0xcd0
? rescuer_thread+0xc40/0xc40
kthread+0x3b3/0x800
? kthread_is_per_cpu+0xb0/0xb0
? lock_downgrade+0x680/0x680
? do_raw_spin_lock+0x12d/0x270
? spin_bug+0x1d0/0x1d0
? finish_task_switch.isra.0+0x284/0x9e0
? lockdep_hardirqs_on_prepare+0x284/0x400
? kthread_is_per_cpu+0xb0/0xb0
ret_from_fork+0x2d/0x70
? kthread_is_per_cpu+0xb0/0xb0
ret_from_fork_asm+0x11/0x20