iommu/vt-d: Avoid memory allocation in iommu_suspend()

iommu/vt-d: Avoid memory allocation in iommu_suspend()

The iommu_suspend() syscore suspend callback is invoked with IRQ disabled.
Allocating memory with the GFP_KERNEL flag may re-enable IRQs during
the suspend callback, which can cause intermittent suspend/hibernation
problems with the following kernel traces:

Calling iommu_suspend+0x0/0x1d0
------------[ cut here ]------------
WARNING: CPU: 0 PID: 15 at kernel/time/timekeeping.c:868 ktime_get+0x9b/0xb0
...
CPU: 0 PID: 15 Comm: rcu_preempt Tainted: G     U      E      6.3-intel #r1
RIP: 0010:ktime_get+0x9b/0xb0
...
Call Trace:
 <IRQ>
 tick_sched_timer+0x22/0x90
 ? __pfx_tick_sched_timer+0x10/0x10
 __hrtimer_run_queues+0x111/0x2b0
 hrtimer_interrupt+0xfa/0x230
 __sysvec_apic_timer_interrupt+0x63/0x140
 sysvec_apic_timer_interrupt+0x7b/0xa0
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1f/0x30
...
------------[ cut here ]------------
Interrupts enabled after iommu_suspend+0x0/0x1d0
WARNING: CPU: 0 PID: 27420 at drivers/base/syscore.c:68 syscore_suspend+0x147/0x270
CPU: 0 PID: 27420 Comm: rtcwake Tainted: G     U  W   E      6.3-intel #r1
RIP: 0010:syscore_suspend+0x147/0x270
...
Call Trace:
 <TASK>
 hibernation_snapshot+0x25b/0x670
 hibernate+0xcd/0x390
 state_store+0xcf/0xe0
 kobj_attr_store+0x13/0x30
 sysfs_kf_write+0x3f/0x50
 kernfs_fop_write_iter+0x128/0x200
 vfs_write+0x1fd/0x3c0
 ksys_write+0x6f/0xf0
 __x64_sys_write+0x1d/0x30
 do_syscall_64+0x3b/0x90
 entry_SYSCALL_64_after_hwframe+0x72/0xdc

Given that only 4 words memory is needed, avoid the memory allocation in
iommu_suspend().

CC: stable@kernel.org
Fixes: 33e07157105e ("iommu/vt-d: Avoid GFP_ATOMIC where it is not needed")
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Tested-by: Ooi, Chin Hao <chin.hao.ooi@intel.com>
Link: https://lore.kernel.org/r/20230921093956.234692-1-rui.zhang@intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20230925120417.55977-2-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>