net/mlx5: Fix command bitmask initialization

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

net/mlx5: Fix command bitmask initialization

Command bitmask have a dedicated bit for MANAGE_PAGES command, this bit
isn't Initialize during command bitmask Initialization, only during
MANAGE_PAGES.

In addition, mlx5_cmd_trigger_completions() is trying to trigger
completion for MANAGE_PAGES command as well.

Hence, in case health error occurred before any MANAGE_PAGES command
have been invoke (for example, during mlx5_enable_hca()),
mlx5_cmd_trigger_completions() will try to trigger completion for
MANAGE_PAGES command, which will result in null-ptr-deref error.[1]

Fix it by Initialize command bitmask correctly.

While at it, re-write the code for better understanding.

[1]
BUG: KASAN: null-ptr-deref in mlx5_cmd_trigger_completions+0x1db/0x600 [mlx5_core]
Write of size 4 at addr 0000000000000214 by task kworker/u96:2/12078
CPU: 10 PID: 12078 Comm: kworker/u96:2 Not tainted 6.9.0-rc2_for_upstream_debug_2024_04_07_19_01 #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
Workqueue: mlx5_health0000:08:00.0 mlx5_fw_fatal_reporter_err_work [mlx5_core]
Call Trace:
<TASK>
dump_stack_lvl+0x7e/0xc0
kasan_report+0xb9/0xf0
kasan_check_range+0xec/0x190
mlx5_cmd_trigger_completions+0x1db/0x600 [mlx5_core]
mlx5_cmd_flush+0x94/0x240 [mlx5_core]
enter_error_state+0x6c/0xd0 [mlx5_core]
mlx5_fw_fatal_reporter_err_work+0xf3/0x480 [mlx5_core]
process_one_work+0x787/0x1490
? lockdep_hardirqs_on_prepare+0x400/0x400
? pwq_dec_nr_in_flight+0xda0/0xda0
? assign_work+0x168/0x240
worker_thread+0x586/0xd30
? rescuer_thread+0xae0/0xae0
kthread+0x2df/0x3b0
? kthread_complete_and_exit+0x20/0x20
ret_from_fork+0x2d/0x70
? kthread_complete_and_exit+0x20/0x20
ret_from_fork_asm+0x11/0x20
</TASK>