iommu/vt-d: Remove unnecessary oom message

Fixes scripts/checkpatch.pl warning:
WARNING: Possible unnecessary 'out of memory' message

Remove it can help us save a bit of memory.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Link: https://lore.kernel.org/r/20210609124937.14260-1-thunder.leizhen@huawei.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20210818134852.1847070-3-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>